Carrickfergus to Ballintoy Coast

It's still the middle of summer, but just beyond Carrickfergus

a year-round industry

is busy stockpiling for the winter.

Alice Roberts is about to venture into an underground world that's never been filmed before.

If you're driving along on an icy winter's night

and your car's not skidding, it's probably because

the gritter lorries have been out.

The rock salt could have come from here - on the coast of Northern Ireland.

'Half a million tons of rock salt are shipped from this little jetty every year.

'This corner of Ireland sits on top of huge deposits of subterranean salt

'that stretch all the way across Europe to Russia's infamous salt mines.

'I don't know quite what I expected from a salt mine,

-'but what I never imagined was being able to drive underground.'

-This was driven in 1965.

'Our guide is Jason Hopps the mine surveyor and, yes, salt of the earth.'

-So how deep does this go down?

-The maximum depth in the mine

is 1,150 feet. This is us just entering the salt now.

-This is all salt crystals?

-Yeah.

We're coming into quite a big cavern. 'There's over 30 miles of tunnels,

'yet only 40% of the rock salt in any area is extracted.

'The rest is left as pillars to shore up the workings.

'The scale of these man-made caverns is amazing.

'Even the largest of the excavation vehicles seem dwarfed.

'Some of the trucks are up to 40 years old,

'but although the atmosphere is salty, it's also extremely dry,

'so they hardly rust at all.'

It's really strange. It's like walking onto the set of a James Bond movie, isn't it?

It's bizarre. How is rock salt actually formed to begin with?

Why is there this seam of salt 800 feet under the surface?

It's basically an old landlocked sea that has evaporated and left the salt behind.

It's happened, in total, five times in this particular area.

We've got a full succession of five salt beds.

At the minute, we're in the fourth deepest, so there's three above us.

-So several sort of evaporated sea beds have been laid down, one on top of another?

-Yeah.

Although we call it "rock salt", it is sea salt? It's just sea salt that's got trapped in rock?

It's sea salt with certain other trace elements.

SIREN WAILS

'We still have to drive down another 300 feet to reach the faces that are

'currently being worked - a full 1,150 feet below ground.

'I've been wondering where everyone is!

'The rock salt is attacked from two directions.

'First, it's undermined with a gigantic cutting blade that takes a ten-foot-deep slice from underneath.

'Then holes are drilled above, ready for explosive charges

'to be inserted deep inside the rock.'

-Can we go a bit closer?

-Yes, we can go down and see.

-This is an undercut.

-Right.

That advances in ten feet, which is the same length as your drill holes.

So this is one of the drill holes

-where you put the explosives in?

-Yes. We pack the explosives in there.

That drill hole's ten-feet-deep by 50-feet-wide by 20-feet-high.

It gives us a full face of 600 tons.

-Really?

-Yeah.

-So when the explosives are stuck in here and they go off,

-600 tons of rock salt falls to the ground?

-600 tons, yes.

SIREN WAILS

'Time to withdraw to a safe distance, I think.'

EXPLOSION

So this is the last stage of the process?

That's been blasted off, hasn't it, that rock?

-Yes. That will have been blasted last night.

-Right.

It'll be taken up to either the crusher or an underground stockpile.

Right.

And where does most of the rock salt from this mine end up?

20% of it or so will end up on Northern Irish and Irish roads.

-Right.

-50 or 60 will go to either England or Scotland,

-and then another maybe 20% to the east coast of the United States.

-Oh, really?

-Yeah.

A little salt can go a long way.

Next time you're snowed in, take a good look at that gritter up ahead.

Chances are that's not any old salt.

It's actually 250 million years old

and comes from 1,000 feet under the Northern Irish coast.

-SEABIRDS SQUAWK

-The further west you go, the wilder this coast gets.

This is a landscape that encourages mavericks.

But it's not an Irishman who stands out from the pack -

it's a Cornishman. An eccentric artist who built his fantasy home out of what he found all around him.

Well, this is what I've come to see - Bendhu House.

Perched on the cliff-top, it looks a bit like a Second World War fort,

but it is actually somebody's house.

'It was in 1936 that Newton Penprase, a Cornish artist,

'first had his dream to build a house to match his vision of this coastline.

'For the next 40 years, he worked almost single-handedly to achieve it.

'Michael and Lorna Ferguson live here now,

'but their first impressions were rather like mine.'

-It's a very strange house.

-Yes. This is the way I remember the house when I'd pass it as a child.

I was fascinated - "What's going on here?

"What is this man building?"

So you'd seen this house as a child and you ended up living in it?

Well, I didn't dream I would ever be living in it.

Nor, at the time, had I any wish to live in it.

Many people loathed Penprase's unconventional design, not least the planning authorities.

But he persevered, using whatever materials came to hand, all picked from the seashore.

In the drawings that he got approved, it says, "all in concrete".

-Right.

-So everything was from the beach initially. He washed the sand

from the water that came down the cliff,

and most of the cement was carried down on his shoulder, down the harbour road.

The bricks were made out of gravel and sand

and he put a lot of extra windows in during the process as well.

'In all, Penprase put in no fewer than 50 windows,

'making the most of Bendhu's panoramic views,

'from Scotland in the east to Donegal in the west.

'When the artist died in 1978, the house was still unfinished,

'but Michael and Lorna have completed his dream.'

That really is a fantastic view, isn't it?

Well, Alice, this is the room that we added on.

The rest is Penprase, but this is what we interpreted

he would have liked us to do with this part of the house.

So if you want to come on through with us...

Right, let's head down below.

Alice, this is the Zodiac room and you'll see why when you look up at the ceiling.

That's amazing.

These are canvases that Penprase painted. He always invited ladies to lie down in the bed,

-to look up, and he would explain all the Zodiac signs.

-Really(?) Right, I see!

It's almost like you're living in an art installation.

Yes, I think that it is. Hopefully, what we've added, Penprase would approve of.

-Would you ever sell it on?

-Oh, no, it's become part of our life.

-What do you think, Michael?

-I'd have to finish it first, but I don't think we'll ever move.

Bendhu House is now a listed building.

Proof that true individuals, like Newton Penprase, can still have the last laugh.

Subtitles by Red Bee Media Ltd E-mail [email protected]