Biscuits Inside the Factory

We're a nation of biscuit lovers.

This year, we'll work our way through enough of them

to fill over 30,000 lorries!

That means we Brits are tucking into 90 million biscuits a day,

more than any other country in Europe.

Whether you prefer them smothered in chocolate or plain and simple,

everyone's got their favourite.

And where's the best place to find out how they're made?

How about the largest biscuit factory in Europe?

I'm Gregg Wallace, and tonight,

I'll join the race to keep up with demand.

Do you know how many biscuits are passing our nose every minute?

Over 3,000.

I'm Cherry Healey,

and I'm going to be making a very expensive biscuit-cutter

out of thousands of pounds' worth of bronze.

And answering the ultimate question.

Are you a dunker or not a dunker?

I get scientific proof that dunking makes your biscuit taste better.

This is not a comfortable biscuit-eating experience.

And historian Ruth Goodman's going back in time

to when biscuits could cure the sick.

"Being full of wind and out of order,

"and there called for a biscuit."

80 million biscuits are baked in this factory every single day.

And we're going to reveal what a mammoth task that is.

Welcome to Inside The Factory.

This is the McVitie's factory in Harlesden, North London,

where 580 workers churn out 2,500 tonnes of biscuits every week!

That's over a quarter of all the biscuits we consume in the UK.

They make 22 different varieties here.

From hobnobs and rich teas to savoury snacks and mini-cheddars.

Tonight we'll learn how they make the nation's favourite,

the chocolate digestive.

Which is nice, because that's my favourite too.

This 50,000-square-metre factory opened back in 1902.

It's been making chocolate digestives since 1925.

The process begins with the delivery of flour,

just as it has for the past 92 years.

Head of intake is Mike Kiley.

Chocolate biscuits start here, do they?

-Yes, they do.

-How much flour in there?

-28 tonne.

-28 tonnes?

And how often does a truck of flour turn up?

-Seven to eight times a day.

-A day?

-Yep.

-Not a week?

-No, a day.

-Shall we get this thing unloaded?

-Yeah. All right, buddy.

-What's that, mate?

-This is a control switch for...

-Are you going to let me do it?

-You can have a go.

You need to press the green button,

take your finger off that and press the yellow button for up.

-So, green button...

-Green button and now the yellow button, below it.

-Wahey! Wahey!

-You've got lift-off.

'That gives me a great sense of power.

'Hydraulics jack the front of the tanker eight metres into the air.'

-That's a beast of a machine, innit?

-Yeah, yeah.

So, I'm now moving 28 tonnes of flour?

-Yeah.

-That might be the biggest thing I've ever moved.

'Gravity does all the hard work

'and the flour falls down towards the back.

'A quick pat of the tank confirms there's no trapped air.'

Yeah, you can stop now.

There's plenty of flour at the back of the tank now.

'Which means we can now blow it through into the factory.'

Push your lever down. That'll allow the flour to travel.

Go for it. With all your might.

'Our biscuit production line begins.'

Yes!

'A pneumatic pump pushes the flour out of the tanker

'and into a 40-tonne silo in ingredients intake.'

How long is that going to take to unload?

That's going to take about an hour and 15 minutes.

-All right, we'll leave you to it.

-Thank you very much.

-Shall we go to the office?

-Can I see the next stage?

-Yeah.

-Cheers, mate.

-Thank you very much.

I'm heading upstairs to the nerve centre of the factory.

Wow! Looks a little bit like the NASA command centre.

These computers monitor the colossal stocks of ingredients.

Is each one of these an actual silo?

-Yes.

-The biggest one is the flour, right?

Yeah, which is 390 tonnes.

Right. And that will last you how long?

-Two days.

-That's only two days' worth of biscuits?

-Yeah.

Every 24 hours,

20 trucks arrive with ingredients from right across the country.

For my digestives, I'm going to need oil, sugar,

glucose, salt and syrups.

How do you know how much you have to order for the next day?

We don't order.

-What happens, then?

-Each one of our suppliers has access

to see what's inside the tanks, and when they've got an empty tank,

-they're sending a delivery.

-I think that's a brilliant system.

It's like having a little camera inside your cupboard saying,

-"We've run out of biscuits..."

-Get some more!

And the supermarket sends the biscuits along!

-Yeah.

-Is that right?

-Very true.

An hour and a quarter after it arrived, my flour is unloaded.

The computer screens confirm

that everything else is ready and waiting.

I've now got nearly all of my ingredients for my biscuit.

However, Cherry, where's my chocolate?

It's being prepared 200 miles away at this refinery in Manchester.

I'm going to make a batch of chocolate for Gregg's biscuits

with factory manager, Dee Smith.

-Hi, Dee!

-Hi, Cherry.

-Lovely to meet you!

-Welcome to Manchester.

-Thank you so much!

So, this is where you cook the chocolate?

Well, this is where we make the chocolate.

There's no cooking involved.

So, it's a process of mixing, refining,

and a very special process called conching.

But this is no ordinary chocolate.

No, it's a really special chocolate for coating biscuits,

so that when you put it in your mouth, it melts.

So, we've got 1,500 kilos of mix in here.

And it's just about ready to discharge.

-Oh, here we go!

-Are we ready?

-Something's happening!

Oh!

-Right, let's have a peek.

-Whoa!

-SHE YELPS

-Wow!

-It's so... Look at that!

-SHE LAUGHS

'This is a rough mix of cocoa, sugar,

'milk powder, oil and vanilla.'

It doesn't feel like

it's sticking your hands into chocolate, that's for sure.

It does remind me of something else, I'll be honest!

It's very granulated at this stage. It's quite rough.

Dee, that is one of the most beautiful smells on Planet Earth,

-but I've got to say...

-Smells better than it looks!

..it smells better than it looks!

-Can I taste it?

-Yes, you can.

It tastes like chocolate sand.

That's a really good description, actually.

And that's why we need to get the particle size

much, much, much smaller.

The sugar crystals are currently the size of the granulated sugar

you buy in the shops.

To make the mix smoother,

it's dropped down 16 feet, into machines called refiners.

This is the first stage of the refining process.

Here, the grainy mix is crushed by a series of giant rollers

into tiny flakes.

And it reduces the particle size down from 1.5mm

that we saw upstairs, down to 0.05 of a millimetre.

That actually increases the surface area and therefore,

it goes from becoming like a slurry and into a powder.

The next process, called conching,

will transform the dry powder into molten chocolate.

OK, Cherry, this is conching.

It is Willy Wonka! Yes!

In here, there's six tonnes of chocolate

and it gets mixed for six hours.

With huge blades, almost like a Mississippi riverboat!

Absolutely, but it's much more aggressive than that.

Liquid cocoa butter has been added to help the chocolate

spread evenly on top of our biscuits.

Astonishingly, the chemistry of this process

is still not fully understood.

But it makes a big difference.

The endless churning releases flavour compounds,

making the chocolate taste rich and velvety.

# Oh, yeah! #

But if you beat it for too long, you get a flavour that's different.

And that's one of the signatures of our chocolate,

is mixing it just right to get that correct flavour

and the correct thickness of the chocolate.

# Beautiful! #

After six hours, my chocolate is shiny and smooth.

But it's not going anywhere

until it's been thoroughly tested by refinery veterans Carla and Eva.

Using a technique called laser diffraction,

they fire laser beams at the particles in the chocolate

to check they're the right size.

But the machine doesn't get final approval.

Carla and Eva have to conduct a chocolate taste test

to check its consistency.

So, what are you looking for when you test chocolate?

Yes, we have to test the viscosity,

so that you know that it's going to coat the biscuit correctly.

And hold the shape of the design on the top.

There we go.

Oh, fresh out the conch.

Just dip it in and try and put it in the middle of your tongue.

-OK.

-And leave it there.

-SHE CHUCKLES

That is just the most gorgeously sweet and rich and smooth chocolate.

So, all that sugar has been refined.

Are you not sick of chocolate?

I'm not sick of chocolate, but I can never go to a party

because if I see a chocolate fountain,

it just reminds me of work.

So, no fondue and no chocolate fountains, thank you very much.

Now, my chocolate's ready for its 200-mile journey to London.

To make sure it doesn't solidify in transit,

it's pumped into a specially heated tanker.

The lorry is specifically designed to ensure

that the temperature's kept at 50 degrees centigrade

for the entire journey.

So, is the lorry like a huge hot thermos of chocolate?

How much is the chocolate in this lorry worth?

About £50,000 worth of chocolate in a tanker like this.

-Liquid gold.

-Yeah, absolutely.

26 tonnes of liquid chocolate heads out on its way to the factory.

Just one of 14 trucks making this four-hour journey every week.

And after a trouble-free trip,

it's ready and waiting for me in the wet ingredients area.

Factory manager Nina Sparks is showing me round.

Nina, this is big.

This is, and this is where the chocolate

comes into the liquids block.

So, it's a big pump here,

chocolate's connected up on the outside

and it's pumped into one of these six tanks.

-How much chocolate?

-Each tank's probably got about 26 tonnes in.

We can hold about 160 tonnes at any one time.

Chocolate is the most expensive ingredient needed for my biscuits.

It costs around £2,000 a tonne,

so Nina and I are currently surrounded

by about £320,000 worth of the stuff.

I can show you the top of one, if you want to.

I can look into a tank of chocolate?

You can come and see 26 tonne of chocolate, Come on.

-Has anyone ever sort of paddled in it?

-No!

Can I dunk in it, just up to my knee?

-No, you can't.

-No? Are you sure?

Each silo is 12 metres tall

and kept at a constant temperature of 55 degrees Celsius

to ensure the chocolate stays liquid.

You can't just heat it back up again?

It would take a really long time.

Once chocolate goes hard, it takes a lot of energy,

a lot of heat, to get it back to being liquid again.

Do you want to have a look in?

Wow!

Yep! That's where I want to go.

-Can't I just get a ladle of it out?

-No.

-Why? Why can't I?

I'm not coming out!

I like it in here.

In the next 24 hours,

they'll get through over two silos' worth of liquid chocolate.

Right, got the dry ingredients, now I've got my chocolate.

-Can I go and make some biscuits?

-Let's go.

-Come on!

I'm going to be one of the best biscuit-makers you've ever seen.

You are!

Next door is the mixing hall.

Here, I'm going to make my batch of dough.

It's a two-stage process, and the first is called creaming up.

We've got 11 mixers up here

and this mixer here is the one we're going to make

-your batch of biscuits on.

-Are they waiting for this now?

-They are waiting for us. We've got to get on.

-Seriously?

We need to go and start the mixer.

I need you to press that green button now.

-Is that all?

-Just the green button.

-And that's going to make it start?

Don't mess it up, Gregg, just the green button.

-You want to start this, don't you?

-I do.

It's just started its process and it will be dropping

all the different ingredients it needs into the bowl right now.

The wet ingredients - fat, water and sugars -

are dropped into the hopper and mixed together for 90 seconds.

That is just like a great big mixing bowl, isn't it?

-Same as the bowl at home.

-Exactly.

Do you know how many biscuits that will make?

-60,000.

-60,000 in each batch?

-That's right, yeah.

That's fantastic. Right, now what happens to it?

Right, so, now we're ready to do our dough-up.

-You honestly call it a dough-up?

-We do.

This is where we add our flours, so we've got white flour,

wholemeal flour and a touch of salt.

-Cream-up, dough-up?

-Correct.

Do you get a biscuit-up, eventually?

Well, we hope so, yeah.

'My flour, along with the other dry ingredients, drops down from above.

'Another 17 minutes of mixing and my dough is done.'

-Whay!

-Yay!

-Now, that looks like a biscuit batch.

-That's right.

So, we've got to do some checks on it first,

so if you open the door for me.

Right.

Can you put the thermometer in it, please, Gregg?

-Why?

-Because if it's too cold,

then the dough will be too crumbly

and we won't be able to form a biscuit.

And if it's too hot,

it'll be too sticky and it will not run through our equipment.

-What temperature do you want?

-I want it to be between 24 and 28.

-What is it?

-26.

Perfect, right.

I've now got 850 kilos of dough

ready to turn into digestive biscuits.

Digestive - that's quite an odd name for a biscuit, isn't it?

Ruth has been checking out its origin.

We all know these instantly as digestive biscuits,

but I'm not sure that my doctor

is going to be prescribing them any time soon.

So, where did this association with digestion come from?

'Medical historian Professor Louise Hill Curth...'

Ruth! Good to see you!

'..tells me that 500 years ago,

'biscuits were thought of as medicine

'and given to people who were ill.'

So, today, you might be given something really bland

and easy to digest.

Well, in the Tudor period, you might be given biscuits.

Because they were very easy to digest.

They were very light, there wasn't much in them,

and you could have those as part of your recuperation.

So, have we got any sort of references

to people eating biscuits for their health?

Lots. Lots and lots.

'One of them is from the mid-17th-century diarist

'Samuel Pepys, in his entry for September 1665.'

"Being full of wind and out of order,

"and there called for a biscuit."

"My digestion's all up the Swanee and..."

-Well, wouldn't you?

-"I need biscuits!"

-Yeah!

-"Bring me a biscuit!"

And a play from 1662 promoted the medicinal properties

of something called a Naples biscuit.

And in the afternoon, about four or five o'clock,

you must take "Naples biscuit dipped in Hippocras..."

-Which is wine.

-"..which helps digestion much."

That's right, so, you dip it in wine and that helps your digestion.

'These Naples biscuits were quite different

'from the digestives we know today.'

-We've got a 17th-century recipe here.

-Absolutely.

'The ingredients were exotic and expensive.'

Take almonds, beaten very fine.

Was that important, then, the fineness of the almond?

Absolutely. Because you want it really easy to digest,

so you don't want big pieces of something.

We're now going to add wine, OK?

-As much as we need to.

-Medicinal.

-Absolutely.

-You feel much better, don't you?

-I'm feeling better already.

I knew you would.

'Next, we add fine flour and rose water,

'which was meant to be good for the heart.'

The next thing we're going to put in is an entire pound of sugar.

I mean, this is a health recipe!

-It's packed full of alcohol and sugar!

-Well, yes.

'The final ingredient is whipped-up egg white,

'which helps to aerate the mix.'

According to the original recipes,

we need to now put them into tin coffins.

I love that word. It's the word for any pastry case at that period.

-That's right.

-Have you got any tin coffins?

We don't have any, unfortunately, but we do have the next best thing.

'After baking, it's time to give the Naples biscuits a try.'

-Mmm.

-SHE LAUGHS

They are quite unique. Certainly very different

from the sort of biscuit we would call a digestive these days.

-They're very light, aren't they?

-They are.

-Yeah.

Do you feel healthier?

It was another 200 years before the modern digestive appeared.

This 1829 advert in the Manchester Courier

is one of the earliest known references

to a biscuit with that name.

And it says, "J Hutchinson,

"the original introducer and sole proprietor of Abernethy's

"celebrated digestive biscuits..."

'Made to a similar recipe to the version we know today,

'they were still being marketed as a health product.'

The number of things this claims to cure is quite remarkable!

Imagine being able to cure typhoid or scarlet fever

by eating a biscuit!

I mean, this is ridiculous, isn't it?

Er, by modern standards, yeah,

but it is very typical of the 19th century.

When McVitie's introduced their version in 1892,

the focus was more on the taste of the biscuit,

rather than its perceived health benefits.

But the name - digestive - remained.

GREGG: An hour and a half in,

I'm gearing up to make a super-sized batch of 60,000 biscuits.

My dough has made it to the oven hall,

where I'm meeting Lawrence Gathari.

He's worked here for 38 years...

-Hello, Gregg!

-Hello, mate.

..and knows biscuits inside out.

Right, I'm ready to make biscuits.

What happens down here?

Well, down here is the area where we mould the biscuits.

Why do you keep looking up there?

Because in a minute, I want you to get up there

-and tell me what you see.

-Really?

-Yes.

-Up?

-If I'm not back, tell me mum I love her.

-OK, I will.

It's not what I expected.

It's coming down in great clumps,

pretty much like the way snow falls off the roof of your shed, you know?

Well, it's the type of dough that's easily broken up.

There's quite a loose consistency to the dough.

So what we need to do is break it up into small enough clumps,

so it can be evenly distributed into the small hopper.

'The machine that does this is called the kibbler.

'Spinning blades shred the dough and fling the pieces onto a conveyor.

'They are now only moments away from their biscuit-shaped destiny.'

I can see the dough's coming down there.

It's then dropping between two rollers.

The front roller that you can see there

is what we call the moulding roller,

which has the shape of the biscuit cut in silhouette.

I can see this mould shining in a little bit of light.

-Can I get a closer look at that?

-Well, we've got one over there.

-Shall we go and see it?

-Yeah, yeah, yeah.

That is a beautiful thing!

I can see exactly how that works now.

As that turns, the dough is pushed onto it

and that then is cutting the shape

and it's imprinting the name and the holes.

Absolutely right. Well done.

It's very attractive and rather clever.

-Not unlike yourself, mate.

-Thank you, Gregg.

I'm surprised that you mould these biscuits and don't cut them.

At home, you would have a big sheet of pastry

and you would cut each biscuit from it.

Well, here, Gregg, we're making so many biscuits,

this is the only way that we can mass-produce them.

Do you know how many biscuits are passing our nose every minute?

-Over 3,000.

-Is it?

THEY CACKLE

This factory runs 24 hours a day,

stamping out a never-ending river of biscuits.

At this rate, it'll take less than 20 minutes

to mould my batch of 60,000.

What happens to all the little extra bits?

There's a scraper that scrapes the excess dough off them

and it drops into this conveyor by my feet

and it runs into this spiral and fed back in.

Hang on. Things go down a spiral.

These look like they're going up a spiral.

They're designed in a way

that it vibrates to send the product upwards.

That's defying gravity!

-There you go,

-Things don't go up a spiral!

It's amazing what you can do here.

So, obviously, this roller is a crucial bit of biscuit-making kit.

Chances are, this one started life in Wigan, with a man called Alan.

Cherry went to meet him.

Hi, excuse me. I'm looking for Alan.

-Alan Long?

-Yeah.

-He's in unit 5A.

-Hi, Alan!

-Hello, Cherry.

-Nice to meet you.

-Nice to meet you.

'Alan Long creates the rollers

'used in most of Britain's biscuit factories.'

Where is everybody?

There's just me. Everything here, I do.

So, where do we start?

We're going to get a blank roller

and we're going to turn it into a biscuit roller.

All right, let's get cracking.

His one-man manufacturing process

begins with a shiny roller of bronze.

It weighs 400 kilos and costs up to £5,000.

Bronze has been the alloy of choice for artists and sculptors

for millennia, and it turns out it's a favourite of Alan's too.

Why on earth do you use such a luxurious material?

Well, the great thing about the bronze

is it's food-approved, lead-free and also it's very nice to machine.

I really love that this is how biscuits start their life.

It's a thing of beauty.

At the moment. We're going to make it look even more beautiful.

'Today, Alan's making a mould for shortbread biscuits.'

-Up?

-Yes, please.

-Up is up?

'And my first job is to help winch the bronze roller

'into the specialist milling machine.'

Down, down, down.

-Is that right?

-Yeah, perfect.

Who knew this is how biscuits start?

'To avoid wonky biscuits,

'the roller must be perfectly level before the machine starts cutting.

'This measuring tool can detect minute changes

'to the roller's alignment.

'If the needle moves, there's a problem.'

-Perfect.

-It's not moving, is it?

-Didn't move, did it?

-It's perfect.

-That did not move at all.

-Nice and flat. It did not move.

This is such an exercise of precision.

There's going to be no uneven biscuits on Alan's watch.

'The roller's in place, and in the office,

'I get to see the shortbread petticoat tail design

'we'll be cutting into it.'

So, that's a mock-up of what will happen?

This is a simulation of what we see on the machine.

The tool will move in that way and cut out

-that imprint into the bronze?

-Exactly that tool path, yeah.

I mean, that is so intricate.

So, how do you design a biscuit?

Everything's drawn up here on this CAD system.

This one, originally, the customer told me he wanted six segments,

as you can see, with a random docker pattern

and a border outline with the little flutes around.

How did you learn to do this?

Originally, I was in the aerospace industry.

I then decided to use that technology

in the biscuit industry to make that a more modern process.

Could you ever have guessed this is what you would end up doing?

Not at the time, no!

'Alan sends the design over to the milling machine

'and prepares a new drillbit.'

OK, Cherry, it's ready to go.

Turn the feed up, it's 100%.

-100%?

-Come on, memory.

-Memory.

-Search.

-Search.

-Programme 4.

-Yes.

-Cycle start.

-Cycle start. Stand by!

Whoa!

This tungsten carbide drill cuts into the bronze.

It's accurate to within 0.03 of a millimetre.

Wow, that looks so cool!

'It can take up to an hour to engrave a single biscuit design.'

-Do you want to have a look at it?

-So badly!

Oh, my goodness!

So, there's your first petticoat tail done.

-It's unnecessarily beautiful.

-It's great, isn't it?

Considering it's just going to imprint a biscuit.

-It is, yeah.

-It's a work of art!

-Do you like it?

It will go into a machine, it'll make lots and lots of biscuits.

Engraving the 40 moulds wrapped around this roller

will take 40 hours.

Some intricate biscuit patterns, like this custard cream,

can take five days to complete.

-I'm going to leave you to it.

-Right.

But before I go, can I take a souvenir, to see if it works?

-Of course you can.

-Hee-hee-hee!

Here we go, the moment of truth.

Look! That is...

-Beautiful.

-Beautiful.

-I love it. Thank you so much.

-No problem.

'Each finished roller has a lifespan of up to two years,

'in which time it could mould more than 3 billion biscuits.'

Next time you crack open the biscuit tin,

don't forget to take a moment

to appreciate the artistry and technology

that's gone into that design.

Over two hours in,

and I'm chasing my batch of digestives

on their way to a hot date.

So, Gregg, this is where the biscuits enter the oven

on their long journey.

-How long do they bake for?

-Six minutes.

Through the whole strip of these ovens?

The whole strip of these ovens.

The oven's 80 metres long and it's divided into four zones,

because we want certain things to happen at certain stages.

'They bake so many biscuits here, they have 11 ovens,

'each one using as much gas in a day

'as an average household uses in a year.'

Gregg, this is the first zone of the oven...

..and in this zone, what we want to do

is start the biscuits rising and we want to start releasing

some of the moisture off from the biscuit.

-So, what temperature is this one?

-This is 180 degrees.

-Is it?

-We don't want it too hot because if it's too hot,

it will coat the biscuit,

it'll seal in the moisture and it will just break apart.

-Can we have a look inside?

-We will.

Right. They have risen probably twice their size.

They have.

The next zone ramps up the temperature

to more than 250 degrees Celsius.

The high heat forces the remaining moisture out through the 18 holes

stamped into the top of the biscuits.

So, up here, the biscuits have fully risen,

we've baked all the moisture out to within spec

and we're looking at 2.2%.

And the biscuits are starting to colour.

-They most certainly are. Fantastic. Can I have a smell?

-Course you can.

Mind you don't burn yourself!

That's smelling like biscuits!

The conveyor runs at just under one mile per hour...

..giving each digestive precisely the same time in the oven.

And that is just a wonderful, constant floating river of biscuits.

It is.

# When ol' man river... #

And now the river takes a surprising diversion.

Because the modern production line

has reached the walls of the old factory,

it needs to make a 180-degree turn.

# ..just keeps rollin' #

It's called the Power Bend, and it's been here for almost 30 years.

-# Doo-doo-do!

-Keeps on rollin'... #

Biscuits on the outside of the curve

travel three times faster than those on the inside.

Do you think we've made the perfect biscuit?

I don't know, I haven't eaten one. They look good.

'My biscuits have made it through the oven,

'but now face a battery of tests.'

We're going to take a biscuit off the line and measure the diameter.

'If they're the wrong size, they won't fit in the packets

'and the whole batch will be recycled as animal food.'

If it fits in there, the biscuit, the diameter's too small.

No!

And if it fits in there, it's just right.

That is beautifully simple.

I like that. Like that. Right, now what?

I want you to take nine biscuits.

I've got one, right.

Whoa, they're hot!

Add them to the nine biscuits

that we got from the other side earlier...

-Making sure the oven's cooking them evenly?

-That's it.

'This is the stack height test,

'which checks the biscuits are the correct thickness.'

What length should the 18 biscuits be?

-We're looking at 130 millimetres.

-130.

That's just short of 130.

We allow plus and minus one millimetre.

-Right.

-So, if it's 129, it's spot on.

Yeah, you're there. You're there.

So far, my biscuits are doing OK, measuring up at 7.2mm each.

They're up to standard and ready to move on.

Do you know what you need, don't you? I think.

You need, like, a quality taster, someone with an expert palate.

Exciting moment coming up!

It's almost time to put the chocolate on my biscuits.

But as Ruth's been discovering, historically,

biscuits were more about survival than pleasure.

A certain town in Berkshire was at the heart of it all.

100 years ago, Reading was home

to the world's biggest and most famous biscuit manufacturer,

Huntley & Palmers.

The town was dominated by the 24-acre mega-factory,

that churned out more than 400 different types of biscuits.

But they became notorious for just one of them.

'I've come to Reading Museum to meet curator Brendan Carr...'

Nice to meet you!

'..who has some examples of the original biscuits

'that gave the company a bad press.'

Oh, wow!

Now, they look like a very plain sort of biscuit!

That's hardtack biscuit.

What exactly is hardtack?

Well, hardtack is just a straightforward recipe -

it's basically flour and water, a little pinch of salt.

These simple biscuits were easy to transport.

So, a good source of nutrition for adventurers and the military.

Captain Scott took Huntley & Palmers hardtack biscuits

to the South Pole in 1910.

Two years later, the company was the natural choice

to manufacture and supply the biscuit rations

issued to British soldiers in World War I.

I can see the word "army" printed here -

"Huntley, Palmers, Army Number Four."

Precisely, yeah.

There were different varieties of ration biscuit.

When people said to you, "Your rations will be biscuits,"

in your head, you'd have been thinking of

the biscuits you'd had at home.

You'd be thinking of things like bourbon creams.

You know, rich tea biscuits,

and then you're suddenly faced with that.

Exactly. But the British Army had to get the men fed,

so this was like a replacement for the bread

that the working classes would have been used to.

And typically, what would happen is you would break it up

with a bit of condensed milk, maybe a bit of jam if you're lucky,

stir it up and make a bit of porridge for yourself.

So, you wouldn't take it, dunk it in your tea and go, "Oh, yum, yum."

No. It's quite far removed from that.

Five million British Tommies were supplied with these biscuits.

But they weren't exactly popular

and the soldiers found inventive uses for their uneaten rations.

Soldiers used to take these biscuits

and fashion them into a little bit of, sort of, trench art.

These have survived because they were sent home as souvenirs.

"Have gone on hunger strike. Reason attached.

"Mind your toes." SHE LAUGHS

These biscuits were so disliked,

they became a common topic for soldiers writing home.

-Hello. Nice to meet you.

-Lovely to meet you.

Rhys David has some letters his father sent from the Front in 1915.

He signed up as a very young man, on his 17th birthday,

and from there he was shipped out to Gallipoli later that year.

So, he was definitely one of those who was supplied

with Huntley and Palmers biscuits.

Yes, he writes about the biscuits

and indicates that he wasn't very happy with them.

He calls them "those blamed biscuits".

In fact, he refers to the problems faced by soldiers

who'd lost their teeth.

I can quote to you from this.

"We sure have had our fair share of them hateful H&Ps..."

Huntley and Palmers.

"Jolly glad I've got a decent lot of ivories to tackle them

"because fellows with false 'uns don't half cop it.

"Blooming near starved and got to break 'em up with pliers

-"to nibble at 'em."

-Oh, my goodness!

But just how bad were these hardtack biscuits?

As a surprise for Rhys, I've got some, made to the original recipe.

-Would you like to try a hardtack biscuit?

-Oh, thank you very much.

-Not 100 years old?

-Not 100 years old!

I mean, they're all right, aren't they?

They're not exciting, but they're OK.

If I hadn't eaten for a few days and I was presented with one of these,

I wouldn't be too upset.

But I think if I was presented with these for several days in a row,

-then I would get pretty cheesed off.

-That was all you were getting.

-Day after day, yeah. Not horrible.

-They're not horrible

but I think I'll still go for rich teas!

SHE LAUGHS

GREGG: At the factory, my 60,000 digestives

have been baked to perfection.

And now there's just one ingredient missing.

Here, Gregg, the biscuits are on their journey from the oven.

They're going to travel half a kilometre to the enrober.

-Enrober?

-Enrober.

That's the machine that puts chocolate onto the biscuit.

That's my sort of machine, that is, sir, my sort of machine.

This epic 500 metre journey

is an essential part of the manufacturing process.

As they saunter along at a sedate 25 metres a minute,

my biscuits are gradually cooling down,

from 90 degrees Celsius when they leave the oven, to under 30.

This means that when the chocolate is applied,

they'll be the perfect temperature for it to solidify.

We want to check that the temperature of the biscuit is correct.

Lawrence, how do you take the temperature of a biscuit?

And what do you do if it's got a cold?

Give it an aspirin!

Right, go on, show me.

Pick a biscuit up.

And...

-Oh, right.

-..fire this thermometer at it.

-Where, there?

-Yeah, press the trigger.

-What have we got?

-25.2.

-And what do you want?

-Between 24 and 28.

My batch has nailed yet another test.

But before we put chocolate on them...

Oh, shut up! That's got to be, that's got to be it now?!

It turns out the chocolate isn't ready.

One final chemical transformation is required

before it's good enough to grace my biscuits.

We've got to make sure the chocolate is properly tempered.

Can I confess something to you? I'm supposed to be a food expert,

I don't actually know what tempering chocolate means.

Have you ever seen a chocolatier when they take some chocolate

-and they pour it onto a slab of marble?

-Yeah, yeah.

And with a palette knife, they move it around.

And what they're doing there is what this machine does,

but on a massive scale.

There's the chocolate coming in...

-Is that that brown line?

-That's that brown line.

-Not very original, is it?!

-No, not really!

And it's slowly getting the right crystals

and getting the chocolate at the right temperature.

The tempering tube scrapes chocolate over a series of plates,

reducing and regulating the size of the cocoa butter crystals.

What would the chocolate be like if it wasn't tempered?

Well, we've got two biscuits here to show you, Gregg.

This is one that was just coated with the untempered chocolate.

It's dull, it melts very easy in the hand.

It looks grainy. That does look like someone's scraped mud on it.

And it's got no sheen.

-Chocolate is a complicated issue, isn't it?

-It's a science.

-It's easier eating it.

-I know.

Makeover complete, the chocolate's ready for its big moment.

I've seen the ingredients come in, I've seen you bake a biscuit,

I've seen you test its size, I've even seen you take its temperature,

I know how the chocolate works.

Can I now please have some chocolate on my biscuit, Lawrence?!

Come on, then, let's have a look.

-Are we finally going to get it?

-We are.

So here, Gregg, the chocolate comes from the tempering tube,

and we form a river of chocolate.

This process is known as enrobing,

a posh name for putting the chocolate on.

I don't really get it, where's the chocolate?

The chocolate is there, that is a river, that's a surge of chocolate.

Oh, I see. The biscuits are coming over,

they're sitting on little metal rafts.

I would've expected the chocolate to be put on the top of the biscuit,

-not the bottom.

-We wouldn't be able to get them on quick enough,

and we only want to coat part of the biscuit.

I'll take a biscuit off there.

It's only that very top part that's got the chocolate on.

If it was poured on, it would completely cover...

-Oh, I see, it can't come down the sides?

-It can't come down the sides.

Is that what's making the ripple effect?

That's the first part of the ripple effect.

The metal wires of the conveyor

press a set of horizontal lines into the chocolate.

The biscuits travel on down the rapids

towards a set of vertical rollers

which imprint another set of lines at right angles to the first.

And it's this that creates the distinctive crosshatched pattern.

I'm getting it. They're falling over it, really, aren't they?

-They are.

-It's a constant waterfall of chocolate biscuits.

As they cool down to 17 degrees Celsius, the chocolate solidifies

on what I now know is the bottom of the biscuits.

For some of us, the perfect accompaniment to these biscuits

is a hot drink to dunk them in.

For others, that's a horrifying idea.

Well, to dunk or not to dunk?

That is the question.

Cherry headed to Nottingham in search of the definitive answer.

Excuse me, excuse me, excuse me.

Can I ask you a question? Are you a dunker or not a dunker?

Dunker or not a dunker?

You don't drink tea?

Not a dunker. Tea?

Coffee, interesting. All right.

Are you a dunker or not a dunker?

So I would say at the moment

Nottingham is 50-50 dunker to non-dunker. Excuse me!

Does that upset you, the idea of it going in there

and getting all soggy?

Dunky-dunk, dunky-dunk...

I love to dunk.

But I want to find out with real science

whether dunking really is the right way to eat a biscuit.

I'm hoping to find the answer at the University of Nottingham,

where Dr Ian Fisk...

Hi, Ian, nice to meet you.

..is going to let me play with his state-of-the-art robot nose.

What we're going to do today is take the biscuits,

chew them and look at the release of aroma compounds into your nose.

And then we're going to take the same biscuit,

we're going to dunk it and see if the aroma release is different.

Every time we eat food, smells, or aromas, are released into our noses.

It's a vital part of how we taste things,

and Ian's machine is so sensitive,

it can detect a single aroma particle

in 1 trillion particles of air.

So you'll be able to tell whether the taste is better

with or without tea?

-Let's find out.

-OK.

So if you want to take a seat,

this probe is going to go slightly up your nose.

OK.

So, breathe quite confidently.

It's just a regular day at the office.

This is not a comfortable biscuit-eating experience!

Next, it's time to test a dunked biscuit.

Will the robot nose detect more aroma particles or less?

This is a big, big moment for biscuits and tea.

All right, here we go. Dunking.

-I would say that's...

-SHE GASPS

-Do they taste different?

-To me, it definitely tastes better.

I can taste the kind of nuttiness and the sweetness better.

But does science agree?

-Let's have a look at the data.

-OK.

So, the trace on the left is the biscuit as you ate it normally.

The trace on the right is when you chewed it

after it's been dunked.

And you can see here the peak is twice as large.

So it's not just a bit better, it's twice as good?

-Yes.

-So are you saying that biscuits do taste better

-when they've been dunked?

-That's true.

So why does dunking a biscuit into tea make it more flavourful?

The aroma compounds and taste compounds can diffuse out

to the mouth and the nose much more efficiently.

So it's not that it changes the taste of the biscuit,

it just allows you to taste it faster and more intensely?

-Yes.

-Science has spoken!

Dunkers are the winners!

So, tea definitely improves the flavour of a biscuit

but could other liquids be even better for dunking?

Time to take this experiment to the streets.

So, it's a very simple game.

All you need to do is take a biscuit...

-Yeah.

-..dunk it, and tell us which of them you prefer.

All right, sound.

In the green mug, we've got tea.

In the blue, we've got coffee.

And in the red is hot milk.

Give it a nice dunk.

Solid dunk, there.

Right, have a little nibble.

-Definitely the green one.

-Definitely green?

That's tea.

-You prefer coffee?

-Every day.

-I'd say coffee.

-Which is your favourite?

-Tea!

-Oh, yay!

-This one.

-Tea was your favourite.

-Mm-hm.

-Tea.

-Tea?

-Every time, tea.

-Every time?

-Every time.

-That one.

-Are you a coffee dunker?

-All the time.

-I think it's the coffee.

-You like the coffee?

People just not dunking in the milk.

They're not feeling the milk.

Which is your favourite?

-Milk.

-Milk!

-Yeah.

OK, it's neck and neck.

Coffee is on four, tea is on four, milk is on one.

So this is the decider.

This is all down to a man called Bruce.

Are you an experienced biscuit dunker?

I love dunking biscuits. Yeah.

This one.

-So, just to confirm, which is your favourite dunking drink?

-Tea.

-Tea!

-Tea.

-Absolutely in the tea?

-Absolutely, 100%.

So they're like the perfect partnership?

Absolutely, they go together like egg and bacon or...

-Jelly and ice cream.

-Fish and chips.

-Cats and dogs.

-Jelly and ice cream, cats and dogs.

Honestly, that's the one.

So the people of Nottingham have decided.

Tea is the best brew for dunking,

but does science agree?

Ian has the results from the same test run in the lab.

Coffee's not far off, but tea was the winner in the lab.

So, in conclusion, in the lab and on the streets,

tea is the dunking champion.

-Absolutely.

-That was a slam dunk.

In London, two hours and 35 minutes

after the flour arrived at the factory,

my biscuits have made it to the packing hall.

Fraser Jones has worked here for 20 years

and he's going to fill me in on the final steps of their journey.

-Fraser.

-Gregg, you all right?

I've watched these biscuits being made every single step of the way.

-Yeah.

-Once they come out into here, what happens now?

Now we need to get them orientated ready for packing.

We've got to do that as quickly and as gently as we can.

We don't want to damage the product.

So what's the first stage? What's this bit?

We've got 18 lanes of biscuits

so the biscuits come onto this air bed

and these diverter arms split all the product into groups of three.

Air bed?

This table here has a big fan underneath

that lifts the biscuits off of the surface

so it cuts out all the friction,

and we have a very gentle and smooth travel.

It reminds me of an air hockey table.

That's exactly the same philosophy.

How many people munching a chocolate biscuit imagine

that they may have floated into the wrapper?

It's like a magic carpet ride for biscuits!

What's the next stage?

We split them into a further three channels, so these shakers...

..divide the biscuits so we've now got six groups.

So you can see, they're all interlocking

and they're being presented perfectly to these slopes.

Shaking dividers jostle the biscuits

so they can make the perfect landing.

One on top of the other.

So they'll fall down this slope one by one and not two at the same time?

-Correct.

-Oh, my word!

Who designs this stuff?

I've been following these biscuits all the way along the line.

Can I finally get to eat one?

As it's you, Gregg, you can have a taste. Why not?

I've waited a long time for this.

Worth waiting for.

At last! Well worth waiting for.

As the digestives arrive at the end of this ingenious machine,

they're divided into groups of 18 biscuits, ready for each packet.

Then they're wrapped in a polypropylene sheet.

Heated rollers seal the bottom and each end.

-Where's it being cut?

-Well, if you just look here, Gregg...

you've got two shafts with heated knives, if you want,

and that creates the seal

and they're perfectly timed to cut the packet

exactly in the middle of each stack of biscuits.

And if that goes wrong,

it starts cutting the packets of biscuits in half?

Oh, yeah. Makes a right mess.

-And it does happen, right?

-Oh, yeah, occasionally.

My batch of biscuits is now safely housed

in more than 3,000 individual packets.

Suckers lift and pack them into 277 boxes

and then it's a quick seven-minute trip

down a biscuit superhighway to dispatch.

It's a land of robots, overseen by one man -

Marcus Pymer, supply chain manager.

Whoa!

Now, this is a crazy room.

Eight tangerine-coloured robots, right?

-Yeah.

-And they're all packing a different brand of biscuits?

Yes, they are.

As my digestives arrive, they're all mixed up with other boxes.

This 115-year-old site is too small to send eight production lines

straight into dispatch on their own conveyors.

So they're merged onto just two lines

and my boxes have to join the queue.

-How does it work?

-It's a bit like an airport baggage handling system.

On the case, you have a QR code.

I've got a camera that takes a picture of the code.

Once it's taken the picture,

the system knows which robot to put the case onto.

My chocolate digestives are identified,

separated out from the other types of biscuits,

and directed towards the correct packing robot.

Each one is named after a London station.

Which station has got my chocolate biscuits?

Your chocolate biscuits are being produced on St Pancras.

No, I want that changed. I'm not happy with that.

As a south London boy, that's disappointing!

Each robot can pack 800 boxes an hour,

stacking them in pre-programmed patterns

and loading them onto pallets.

From there, there's a signal sent to the two travel carts in the middle,

so one will come down, pick up the full pallet and take it away.

While it's taking the full pallet away,

another cart will bring an empty and put it in its place.

These are the pallets I've seen put together by the robots, yeah?

-That's correct, Gregg, yes.

-Right, and what stage is this, then?

So this is just getting ready to load them onto the trailers

-that are behind you, Gregg.

-But where do you store them all?

I don't. So basically, they come off that automated palletisation system,

come on to here and then my forklift driver will load them

onto the trailer behind you, and they go off.

-So as soon as they're made...

-Yeah.

-..they're boxed...

-Yeah.

-..palleted and out?

Yes.

-No warehouse storage at all?

-No.

They only have enough space here

to store two hours' worth of freshly baked biscuits.

How many lorries go out of here?

We average about 34 trailers every 24 hours.

Nearly one and a half every hour?

-Yes.

-And what do you have nightmares about?

-What worries you?

-Um...conveyors going down.

Trailers not turning up.

-Weather.

-Why the weather?

Because we can't load your chocolate digestives if it's too hot,

because it melts the chocolate.

The one good thing about this, if you have any hold-up at all,

-you can have a cup of tea and a biscuit.

-Correct.

From here, the chocolate digestives head to a distribution centre

and off to the shops.

84% are consumed in the UK.

People in Sheffield and Glasgow are the biggest biscuit lovers,

but Lancashire munches more chocolate digestives

than anywhere else.

I'm a Londoner and I had no idea in London was a factory

churning out 13 million chocolate digestives every 24 hours.

I certainly didn't expect to see them

floating along on their own air bed.

But what I learned that really surprised me

was they put the chocolate on the bottom of the biscuit.

Who knew?

Raj, take it away, mate.

It's taken a touch over four hours, but my biscuits are out and about...

..heading towards the shelves of a shop near you.