0:00:37 > 0:00:40All my working life, I've been involved
0:00:40 > 0:00:42with church towers and steeples.
0:00:42 > 0:00:47This is one of the finest in the land: St Warberg's in Preston.
0:00:47 > 0:00:49It's 311 feet high.
0:00:49 > 0:00:54They reckon it's the tallest church steeple in England.
0:00:54 > 0:00:56Not the tallest cathedral one.
0:01:11 > 0:01:14Such a beautiful needle point.
0:01:14 > 0:01:16Big nut and bolts holding t'top on.
0:01:16 > 0:01:19Otherwise, it would blow away in the wind.
0:01:19 > 0:01:24I think, really, getting to the end of my days as a steeplejack,
0:01:24 > 0:01:28I think it may be the last big steeple I'll ever mend.
0:01:33 > 0:01:37Man has been using stones to build places of worship
0:01:37 > 0:01:41for thousands of years. The origins of the oldest
0:01:41 > 0:01:45are shrouded in mystery. The best-known is Stonehenge.
0:01:45 > 0:01:49But not far away, at Avebury,
0:01:49 > 0:01:53I went to see one that was built on an even grander scale.
0:01:59 > 0:02:06This is one of the oldest megalithic monuments in Europe. It's older than Stonehenge.
0:02:06 > 0:02:11It were developed, so they say, somewhere roundabout 2500
0:02:11 > 0:02:13to 2200 BC.
0:02:13 > 0:02:16The whole site covers a vast area.
0:02:16 > 0:02:20You can actually see some of the earliest examples
0:02:20 > 0:02:24of building and construction work in all of Great Britain.
0:02:24 > 0:02:28This great trench covers three-quarters of a mile
0:02:28 > 0:02:30and is 15 feet deep.
0:02:30 > 0:02:33It's one 'eck of an achievement,
0:02:33 > 0:02:36for four-and-a-half thousand years old, eh?
0:02:36 > 0:02:40Its huge size and the depth of the ditch...
0:02:40 > 0:02:42It will have lost depth,
0:02:42 > 0:02:49when you think of all the years and the erosion and the washing of the stuff back down the hole.
0:02:49 > 0:02:51Yes, we know from excavations
0:02:51 > 0:02:54we can only see the top third of the ditch.
0:02:54 > 0:02:57A lot of in-fill has slumped in over the centuries.
0:02:57 > 0:03:00Now then, how did they do it, so long ago?
0:03:00 > 0:03:04Well, simple tools, Fred, but well-organised labour.
0:03:04 > 0:03:07What have we got here?
0:03:07 > 0:03:10The most important tool that survives
0:03:10 > 0:03:12is the red deer antler pick.
0:03:12 > 0:03:18They could have had other tools, wood and basketry, that wouldn't survive.
0:03:18 > 0:03:20But this is the one so widely found
0:03:20 > 0:03:23on these early prehistoric sites.
0:03:23 > 0:03:27But it's important not to think of it as a pickaxe.
0:03:27 > 0:03:29It hasn't got the weight.
0:03:29 > 0:03:32It's not like how WE use a pickaxe.
0:03:32 > 0:03:35On prehistoric antlers, the back of the coronet
0:03:35 > 0:03:38is often heavily battered, on worn examples.
0:03:38 > 0:03:42It suggests they used a mallet to drive the point in,
0:03:42 > 0:03:45then used it as a levering tool.
0:03:45 > 0:03:49These ox shoulder blades are sometimes found on these sites.
0:03:49 > 0:03:53They've always been cited as the equivalent of a shovel,
0:03:53 > 0:03:58but it's questionable whether they would shift enough material
0:03:58 > 0:04:02- and whether you'd have enough leverage.- How many stones
0:04:02 > 0:04:07do you think there were in the whole circle, all together?
0:04:07 > 0:04:11We think there were 98 stones, 98 or 99, in the outer circle.
0:04:11 > 0:04:15Then there are the smaller features of two inner circles.
0:04:15 > 0:04:19Each stone stands in a pit, about three feet deep.
0:04:19 > 0:04:23They're really just balanced in position
0:04:23 > 0:04:25and held by smaller chock stones.
0:04:25 > 0:04:29It's very similar material to Stonehenge.
0:04:29 > 0:04:32They are the same. Sarsen stone, it is.
0:04:32 > 0:04:35The difference is that these aren't shaped.
0:04:35 > 0:04:42They're selected for shape, perhaps, but not worked and shaped like they are at Stonehenge.
0:04:47 > 0:04:49Is there any estimate at all
0:04:49 > 0:04:53of how many men were involved in this operation?
0:04:53 > 0:04:56It's very difficult to estimate,
0:04:56 > 0:04:59because we don't know the length of time it took
0:04:59 > 0:05:02to complete a monument like this.
0:05:02 > 0:05:06We can't define it as less than a hundred years, or something.
0:05:06 > 0:05:10There's no written record, in any shape or form.
0:05:10 > 0:05:12- Not at all.- There's nothing.
0:05:12 > 0:05:16They just left us with this big circular trench.
0:05:16 > 0:05:18A mystery.
0:05:20 > 0:05:25Avebury has been an important place of worship for 4½ millennia.
0:05:25 > 0:05:28As well as the pagan stone circle,
0:05:28 > 0:05:31there's also an early Christian church.
0:05:31 > 0:05:35St James's dates from the time the Anglo-Saxons were first
0:05:35 > 0:05:38converted to Christianity,
0:05:38 > 0:05:42but it was much altered and added-to in the Middle Ages.
0:05:42 > 0:05:47It's quite rare to find one that's remained completely unaltered.
0:05:47 > 0:05:49To see one of the few that remain,
0:05:49 > 0:05:54I travelled up to Escomb in County Durham.
0:05:55 > 0:06:03This Saxon church at Escomb is one of the oldest churches in all of Great Britain.
0:06:03 > 0:06:11It was built from the remains of an abandoned Roman fort at Binchester, somewhere in the locality.
0:06:11 > 0:06:14No-one really knows who built it,
0:06:14 > 0:06:19how long ago it was built or why it was built in this particular spot.
0:06:19 > 0:06:22One of the people who helps to keep the church alive
0:06:22 > 0:06:26is Lillian Moody. She knows every inch of it.
0:06:26 > 0:06:30The actual corners of the building, if you look,
0:06:30 > 0:06:35- slope slightly inwards... - Yes, indeed.- ..for maximum strength.
0:06:35 > 0:06:40Crow step gable end, isn't it? In architectural terms.
0:06:40 > 0:06:43There's a Roman altar stone...
0:06:45 > 0:06:47- up there. Can you see it? - Yes, I can.
0:06:47 > 0:06:51With a rosette. They think that it's Mithras.
0:06:51 > 0:06:54Mithras was very popular with Roman soldiers,
0:06:54 > 0:06:59being the god of courage and bravery.
0:06:59 > 0:07:02Now, the doorway is beautiful.
0:07:02 > 0:07:06The jambs are interesting, the big stones going in,
0:07:06 > 0:07:09and then two small ones.
0:07:09 > 0:07:13There are bits of tile underneath that take the play up.
0:07:13 > 0:07:15- Can you see the plaster?- Yeah.
0:07:15 > 0:07:20- That's original Anglo-Saxon plaster. - It were all over that once.
0:07:20 > 0:07:24The churches were plastered inside and out.
0:07:24 > 0:07:27Now, if you have a look here, Fred...
0:07:27 > 0:07:29The chancel is not keyed in.
0:07:29 > 0:07:32No, it isn't. It's just leaned on.
0:07:32 > 0:07:34Clagged on, as we say in Durham.
0:07:34 > 0:07:37- Just propped up against it? - Just propped up.
0:07:37 > 0:07:41Well, Lillian, does anybody really know how old it is?
0:07:41 > 0:07:43Not really.
0:07:43 > 0:07:45There's no records at all.
0:07:45 > 0:07:49We THINK about 675.
0:07:49 > 0:07:52Now, it could be 20 years either way.
0:07:53 > 0:07:57The roof, Fred, if you notice, is extremely high.
0:07:57 > 0:08:02- Not the original.- It would be a thatched one at the beginning,
0:08:02 > 0:08:04- made with reeds.- Yes, probably.
0:08:04 > 0:08:09- The most important thing is this arch.- It's Roman, in't it?
0:08:09 > 0:08:13The Romans knew how to build arches,
0:08:13 > 0:08:17but the Saxons had lost the art and didn't know.
0:08:17 > 0:08:21So, they had to bring that rounded part intact.
0:08:21 > 0:08:24That, where it's a rectangular cut...
0:08:24 > 0:08:30The Romans used it to put a tool in, a lewis, to lift the stone. The Saxons didn't know why.
0:08:30 > 0:08:34The Romans were more advanced than the Saxons.
0:08:34 > 0:08:40Really, they were marvellous engineers, when you think of what they've done...
0:08:40 > 0:08:45In the Middle Ages, their engineering skills began to appear.
0:08:45 > 0:08:48At Chester Cathedral, most of the building work
0:08:48 > 0:08:53was done between the 11th and 15th centuries.
0:08:53 > 0:08:57BELLS CHIME
0:09:00 > 0:09:04It started its life as a Benedictine monastery.
0:09:04 > 0:09:07It was dissolved by Henry VIII in 1540.
0:09:07 > 0:09:10A year later, he gave it back to the Church
0:09:10 > 0:09:15as the cathedral for the newly-created diocese of Chester.
0:09:15 > 0:09:22So, what we've got in here are some of the best-preserved monastic buildings in England.
0:09:22 > 0:09:24So, this is the cloisters.
0:09:24 > 0:09:29This is where the monks lived - their domestic quarters.
0:09:29 > 0:09:33This is very much as the monks would have seen it.
0:09:33 > 0:09:35This is, of course, a new roof.
0:09:35 > 0:09:38Yeah, the roof is later. This is 1527.
0:09:38 > 0:09:40The earlier one was wood
0:09:40 > 0:09:44and they replaced it with this stone ceiling.
0:09:44 > 0:09:49Up here, you can see clearly where the later roof has been pushed through
0:09:49 > 0:09:53into the earlier work.
0:09:53 > 0:09:56On the ledge would be a trough of running water.
0:09:56 > 0:10:01The monks washed their hands there before their meals.
0:10:01 > 0:10:04And they're big lumps, aren't they?
0:10:04 > 0:10:07Normally, they're quite small pieces.
0:10:07 > 0:10:11- They're almost like great flagstones.- Yes, slabs of stone.
0:10:11 > 0:10:15The carved bosses, as well, are big chunks of stone.
0:10:15 > 0:10:18'Going into the cathedral itself
0:10:18 > 0:10:25'is very good for seeing the way a great cathedral like this has changed over the centuries.'
0:10:25 > 0:10:28This is the main part of the building.
0:10:28 > 0:10:30This is the north transept.
0:10:30 > 0:10:34I think here really shows just what a mixture this building is.
0:10:34 > 0:10:39- Norman arches and Gothic arches... - Absolutely.
0:10:39 > 0:10:44The one on the left is about 1092, part of the original Norman church.
0:10:44 > 0:10:49On the right, it's about 1300, part of the later rebuild.
0:10:49 > 0:10:51It looks like a real mixture,
0:10:51 > 0:10:54but they didn't seem to mind how it looked.
0:10:54 > 0:10:57I suppose the reason for the thick walls
0:10:57 > 0:11:01on the Norman bits is the semicircular arch.
0:11:01 > 0:11:04They needed thicker walls to take the thrust.
0:11:04 > 0:11:07As against the Gothic job, which...
0:11:07 > 0:11:11- All the weight's downwards. - You can do more with a Gothic arch.
0:11:11 > 0:11:17You can go higher, you can vault unequal spaces. It's more flexible.
0:11:17 > 0:11:21A lot of people must wonder how they built arches.
0:11:21 > 0:11:23It's pretty simple, when you think.
0:11:23 > 0:11:26They had support from below
0:11:26 > 0:11:30and built a wooden curve, the same form as the inside of the arch,
0:11:30 > 0:11:35started from each side and worked their way to t'centre.
0:11:35 > 0:11:39It's one reason why woodworkers were so important.
0:11:39 > 0:11:44They didn't just do nice carving. They helped to build the structure.
0:11:44 > 0:11:46When you think of a growing ceiling,
0:11:46 > 0:11:53that must have been a work of art of woodwork, before the massive stones.
0:11:53 > 0:11:57They had to get it right to take the weight, not only the shape.
0:11:57 > 0:12:00I wonder how they felt taking the wood away!
0:12:02 > 0:12:04'I decided to put it to the test.
0:12:09 > 0:12:12'This is a demonstration of building an arch.
0:12:14 > 0:12:18'Arches have been around for thousands of years.
0:12:18 > 0:12:21'The earliest ones, they used earth for the centring.
0:12:21 > 0:12:24'They built outside walls,
0:12:24 > 0:12:28'piled a load of muck up and put timber on top of it,
0:12:28 > 0:12:33'put the masonry over the top of that, then dug the muck out.
0:12:33 > 0:12:36'I suppose, in early days, before Medieval times,
0:12:36 > 0:12:41'that would be the only way that they could work it out.
0:12:41 > 0:12:45The wooden bit in the middle, like this bit down here,
0:12:45 > 0:12:49is known as the centring. Of course, when the thing's set,
0:12:49 > 0:12:52we can withdraw these wedges,
0:12:52 > 0:12:54down here.
0:12:54 > 0:12:58Hopefully, the wood will become slack.
0:12:58 > 0:13:01Then the arch will stay in position.
0:13:03 > 0:13:08I'm very confident that it WILL stay in position.
0:13:08 > 0:13:11I'm not worried about it at all.
0:13:13 > 0:13:15Like...so.
0:13:26 > 0:13:29That's what all good bricklayers do at brew time.
0:13:29 > 0:13:33I'll come back after lunch and take the middle out.
0:13:36 > 0:13:40The Middle Ages was the great age of cathedral building.
0:13:40 > 0:13:44They've left us with some magnificent monuments
0:13:44 > 0:13:48to the skills of the medieval builders and stonemasons.
0:13:48 > 0:13:51One of the grandest of them all is York Minster.
0:13:53 > 0:13:56It was started in 1220
0:13:56 > 0:13:58and it took 250 years to complete.
0:13:58 > 0:14:02One of the great engineering advances of the time was
0:14:02 > 0:14:05the introduction of the flying buttress.
0:14:05 > 0:14:10This was an half-arch, which transmitted the thrust of the roof
0:14:10 > 0:14:14from the upper part of the wall onto an outer support.
0:14:18 > 0:14:21Really, the invention of the flying buttress...
0:14:21 > 0:14:26People may go to cathedrals and think they're a bit ornamental,
0:14:26 > 0:14:29but really they're very important.
0:14:29 > 0:14:33When you go in these great cathedrals, stand on the main aisle
0:14:33 > 0:14:37and look down and there's all these great windows.
0:14:37 > 0:14:40Have you wondered why it doesn't collapse,
0:14:40 > 0:14:44when you see two great rows of pillars, with arches on top,
0:14:44 > 0:14:48then great tall windows, up to t'ceiling nearly?
0:14:48 > 0:14:51And then, of course, the groin stone roof.
0:14:51 > 0:14:54Where does all the shove and thrust go?
0:14:54 > 0:14:59In actual fact, when they invented the side aisles, with groin roofs,
0:14:59 > 0:15:03they built the buttresses outside in t'rain
0:15:03 > 0:15:06and put as much weight on them as they could.
0:15:06 > 0:15:13They built these little half-arches in a ways, like a flying buttress, that holds together
0:15:13 > 0:15:17the solid bits in-between the windows.
0:15:17 > 0:15:21Although they look big and strong from outside,
0:15:21 > 0:15:25they're an unbelievably fragile piece of building.
0:15:25 > 0:15:31When you look at the stonework on the outside of York Minster, it's amazing, the detail.
0:15:31 > 0:15:34You know, the mouldings, the niches,
0:15:34 > 0:15:38the beautiful statues, the window openings
0:15:38 > 0:15:41and the tracery in the windows.
0:15:41 > 0:15:45The detail around this great west doorway is summat else.
0:15:45 > 0:15:48I mean, it's brilliant.
0:15:48 > 0:15:51People say, "Pity they can't do it now."
0:15:51 > 0:15:53But I'm afraid they're wrong.
0:15:53 > 0:15:56Most of that up there were made in a yard,
0:15:56 > 0:15:59just round the back of the Minster.
0:16:00 > 0:16:06Before they chisel away at the stone, detailed drawings have to be done.
0:16:06 > 0:16:09From the drawings, they make a template,
0:16:09 > 0:16:15which the stonemason uses to carve out the basic geometric shapes.
0:16:15 > 0:16:17- Can I have a go?- Certainly.
0:16:17 > 0:16:20You won't hit me if I break it, will you?
0:16:20 > 0:16:23Thank you. Right...
0:16:28 > 0:16:33They reckon Michelangelo could shift more rock in a day
0:16:33 > 0:16:35than two normal men.
0:16:40 > 0:16:43This is the geometric masonry,
0:16:43 > 0:16:47which is very disciplined,
0:16:47 > 0:16:50going to definitive lines in the stone.
0:16:50 > 0:16:52It goes straight in the building.
0:16:52 > 0:16:55For embellishments of flowers or leaves,
0:16:55 > 0:16:58it goes into the carvers' workshop.
0:17:05 > 0:17:08Now then, good afternoon, Martin.
0:17:08 > 0:17:11- Hello, Fred.- I can see now
0:17:11 > 0:17:16the three stages of making them beautiful leaves on the side.
0:17:16 > 0:17:18It must take a long time.
0:17:18 > 0:17:21How long does it take to do three leaves?
0:17:21 > 0:17:24There's probably another week's work there.
0:17:24 > 0:17:26When people walk by York Minster,
0:17:26 > 0:17:31they don't appreciate the effort that's gone into it.
0:17:31 > 0:17:33How do you go about making these?
0:17:33 > 0:17:36Heck of a tricky operation.
0:17:36 > 0:17:38A touch delicacy, in't it?
0:17:38 > 0:17:43Once the form of the leaf's shaped, you know where the reference points are.
0:17:43 > 0:17:47Then you can begin to dig behind with smaller chisels.
0:17:47 > 0:17:51Sometimes, to get behind, you can use a drill.
0:17:51 > 0:17:55When it's finished, it will go into the southwest door.
0:17:55 > 0:17:59We met a man downstairs who's making one a week.
0:17:59 > 0:18:03They're knocking them out as fast as we're putting them in.
0:18:03 > 0:18:08I can see originally it were longer. It went right through.
0:18:08 > 0:18:10You've cut it off where it's still good.
0:18:10 > 0:18:15They were a lot bigger than the ones we're putting back in.
0:18:15 > 0:18:19We can't put that size stone in, because we just can't lift them
0:18:19 > 0:18:25to where we want them at the front. They pushed them straight back.
0:18:25 > 0:18:28This is it: the great moment.
0:18:28 > 0:18:30We're now going to strike the arch.
0:18:30 > 0:18:33It's had an hour or two to settle down.
0:18:33 > 0:18:37It is still a bit green, but I don't think we'll have any bother.
0:18:48 > 0:18:50Success! Ha ha ha!
0:18:52 > 0:18:56The Romans and Normans would have done it out of stone,
0:18:56 > 0:18:59but men like Brunel used lots of bricks.
0:18:59 > 0:19:04It looks quite precarious and weak in its present state,
0:19:06 > 0:19:10but if it has pressure coming on it from all the way around the sides,
0:19:10 > 0:19:15the top and ten to and ten past, it goes even stronger.
0:19:15 > 0:19:17You'll never crush it.
0:19:17 > 0:19:21You need immense strength and weight to destroy an arch.
0:19:21 > 0:19:24That's how they got their arches to stay up,
0:19:24 > 0:19:30but how about a huge dome, like the one on St Paul's Cathedral in London?
0:19:30 > 0:19:35During the second half of the 17th century, a great new cathedral was
0:19:35 > 0:19:38constructed in the City of London
0:19:38 > 0:19:43to replace an earlier one, partially destroyed by the Great Fire of London.
0:19:43 > 0:19:49St Paul's Cathedral, designed and built by Christopher Wren, is something else.
0:19:49 > 0:19:54In its heyday, it must have dominated the skyline of London.
0:19:54 > 0:19:56It's a great pity now that
0:19:56 > 0:20:02you can't see it very well, for all the modern buildings surrounding it.
0:20:02 > 0:20:04Before he could build it,
0:20:04 > 0:20:07he had to get rid of the remains of the old one.
0:20:07 > 0:20:12Believe it or not, he tried explosives, but he upset the neighbours,
0:20:12 > 0:20:15so they used a battering ram instead.
0:20:15 > 0:20:19During the 35 years it took to construct it,
0:20:19 > 0:20:23Wren used the finest craftsmen, the best materials
0:20:23 > 0:20:25and supervised the books.
0:20:25 > 0:20:30Every Saturday, he came to have a see how things were going. Later,
0:20:30 > 0:20:33when they got high, he were craned up in a basket
0:20:33 > 0:20:37to the top to survey the dome and all its goings-on.
0:20:37 > 0:20:40The sections that carry the staircases...
0:20:40 > 0:20:47'Martin Fletcher is the Clerk of Works, responsible for the upkeep of the whole structure.'
0:20:47 > 0:20:51It was all about the embellishment of stonework. As you can see,
0:20:51 > 0:20:55at the west end of the cathedral is how HE wanted it.
0:20:55 > 0:20:58Just white and stone and plain.
0:20:58 > 0:21:02And then along come the beautifiers.
0:21:02 > 0:21:06ORGAN MUSIC PLAYS
0:21:10 > 0:21:15All this mosaic work was only done at the end of the 19th century.
0:21:15 > 0:21:22It's very different from the plain, unadorned white that Wren had intended.
0:21:28 > 0:21:34All of the eight pillars carry a base weight, which includes the dome, the colonnade,
0:21:34 > 0:21:39down to the drum bells... 63,000 tons on those eight columns.
0:21:41 > 0:21:46What's this say? It's in Latin. I never went to a proper school.
0:21:46 > 0:21:49You and me both, but the whole thing about it is...
0:21:49 > 0:21:56It says, "If you want to see a monument to Sir Christopher Wren, just look around you."
0:21:56 > 0:21:59Yeah, that's a true fact, in't it?
0:22:05 > 0:22:09St Paul's Cathedral really is a wonderful building.
0:22:09 > 0:22:12When you stand there in London and look at it,
0:22:12 > 0:22:16you imagine it's just a big dome, but it isn't really.
0:22:16 > 0:22:20There are three domes. When you're stood in the bottom,
0:22:20 > 0:22:25you see a beautiful dome, nicely painted, when you look upwards.
0:22:25 > 0:22:31But on t'topside of that, there's a big cone that holds up the lantern on the top.
0:22:31 > 0:22:33Then, stuck to the outside of that,
0:22:33 > 0:22:38there's a load of timber roof trusses that hold yet one more dome,
0:22:38 > 0:22:41which of course has got the lead on top of it.
0:22:41 > 0:22:46These stone corbels support the framework on this great cone,
0:22:46 > 0:22:50which is perfectly straight. You see, looking at that,
0:22:50 > 0:22:53the greatest area of thrust of the whole lot
0:22:53 > 0:22:56is here, on top of these pillars.
0:22:56 > 0:22:59With all this pressure, how do you stop
0:22:59 > 0:23:03the whole thing pushing out on itself and collapsing?
0:23:03 > 0:23:07Wren came up with an ingenious solution.
0:23:07 > 0:23:11He put a great wrought iron chain all around the dome
0:23:11 > 0:23:16and sunk it into a band of stone that went all round the perimeter.
0:23:16 > 0:23:21It was leaded in, as well, by buckets and ladles of molten lead.
0:23:21 > 0:23:24When you think back to the 17-odds,
0:23:24 > 0:23:29the methods of melting lead wouldn't be quite as good as what they are today.
0:23:29 > 0:23:33You can imagine a little lad, with a pig's bladder,
0:23:33 > 0:23:38furiously pumping some bit of a coal fire, or charcoal,
0:23:38 > 0:23:42a crucible stuck on top of it, full of lead.
0:23:42 > 0:23:48They would pour it in. It had set, so the next lot wouldn't adhere to the other lot.
0:23:48 > 0:23:51This has been, really, part of its downfall.
0:23:51 > 0:23:56Now they're repairing the chain and the masonry around it.
0:23:56 > 0:23:59But even now, you see little of the chain.
0:23:59 > 0:24:03All you can see of it are the bits they've got exposed
0:24:03 > 0:24:05in the section they're working on.
0:24:05 > 0:24:08- This is it, then?- This is the chain.
0:24:08 > 0:24:11What they did was come up to this height,
0:24:11 > 0:24:15they cut a chase in all the way around, 150 metres round.
0:24:15 > 0:24:17The chain was forged,
0:24:17 > 0:24:21pockets were dropped in for the couplings,
0:24:21 > 0:24:24and above every column, going all the way round,
0:24:24 > 0:24:29you have two knuckles on there, which are cramps. It's like a fork.
0:24:29 > 0:24:33That goes right the way back to the base of the cone,
0:24:33 > 0:24:37with another two chains, so that's your restraint.
0:24:37 > 0:24:40What's happened, over a period of years,
0:24:40 > 0:24:42where they used to pour the lead,
0:24:42 > 0:24:46because it hits this fairly cold, it laminates.
0:24:46 > 0:24:49Any moisture has got into the chain.
0:24:49 > 0:24:53As you know, if you get a little bit of rust in there, it swells up,
0:24:53 > 0:24:58blows the stone out of the front, resulting in these huge fractures.
0:25:00 > 0:25:03When you think how old St Paul's is,
0:25:03 > 0:25:06it's a credit to Christopher Wren.
0:25:06 > 0:25:11The architecture and engineering involved in it are something else.
0:25:11 > 0:25:14It's interesting that, over the centuries,
0:25:14 > 0:25:17a lot of our best architects, builders and craftsmen
0:25:17 > 0:25:21have reserved their finest work for places of worship.
0:25:21 > 0:25:25They didn't just save it for churches as grand as St Paul's.
0:25:25 > 0:25:28This is St Margaret's Church
0:25:28 > 0:25:31at Bodelwyddan, near Rhyl in north Wales.
0:25:31 > 0:25:33I've always greatly admired it.
0:25:33 > 0:25:36They call it the Marble Church,
0:25:36 > 0:25:42because of all the different types of marble used in the interior decoration.
0:25:42 > 0:25:47Altogether, there are 14 different varieties of marble in this church
0:25:47 > 0:25:53and there's an amazing richness of craftsmanship throughout the whole place.
0:25:53 > 0:25:59Just look at the quality of the carvings and the stained glass.
0:26:04 > 0:26:07The bit that I really like is the steeple.
0:26:07 > 0:26:10You know, the spire. It's a work of art.
0:26:10 > 0:26:15The guy who designed it has the top ¾ of the steeple resting on eight stones.
0:26:15 > 0:26:19How did he know that they'd take the weight?
0:26:19 > 0:26:21Because they're so fine.
0:26:21 > 0:26:24The whole steeple, the tower itself,
0:26:24 > 0:26:28with its double pinnacles on the corners and flying buttresses
0:26:28 > 0:26:34that hold them all together, and all the lovely, fine tracery...
0:26:44 > 0:26:47I passed by here, years and years and years ago.
0:26:47 > 0:26:51I stopped one day and had a look at it - beautiful steeple.
0:26:51 > 0:26:56I always wanted to have a closer look and get inside, where we are now.
0:26:56 > 0:27:01It's interesting, because you can see the eight stones up above,
0:27:01 > 0:27:05that takes the weight of the top ¾ of the steeple.
0:27:07 > 0:27:11If you look to t'top, you can see the iron crosstree
0:27:11 > 0:27:14that the great nut and bolt comes through
0:27:14 > 0:27:16to hold the top on the steeple.
0:27:16 > 0:27:21I think I'll go outside now and have a look round on the verandah.
0:27:21 > 0:27:24You can actually see the lovely curve
0:27:24 > 0:27:26of the barrel shape of the steeple.
0:27:26 > 0:27:30When you're half a mile away, it looks perfectly straight.
0:27:30 > 0:27:34It's actually barrel-shaped, like a barrel of beer.
0:27:35 > 0:27:38These lovely pinnacles on the corners,
0:27:38 > 0:27:45with slender supports fretworked out, and flying buttresses that join one to the other.
0:27:45 > 0:27:47Lovely bit of stonework, really.
0:28:03 > 0:28:08Next week, we'll be looking at places of work, new and old.
0:28:08 > 0:28:13Subtitles by David Van-Cauter BBC - 2000
0:28:13 > 0:28:16E-mail us at subtitling@bbc.co.uk