0:00:27 > 0:00:33Lyme Regis's most famous landmark is the striking harbour wall, known as the Cobb.
0:00:33 > 0:00:38It inspired writers like Jane Austen and was the setting for the classic opening scene
0:00:38 > 0:00:40of The French Lieutenant's Woman.
0:00:40 > 0:00:44But this wall has a far more important practical function.
0:00:44 > 0:00:47For the last 700 years,
0:00:47 > 0:00:50it's stopped the sea from literally sweeping Lyme Regis away.
0:00:53 > 0:00:59The town sits on top of one of the most unstable stretches of coastline in the country.
0:00:59 > 0:01:03The sea and the insecure ground underneath the town
0:01:03 > 0:01:06conspire to create huge landslides.
0:01:06 > 0:01:12The residents of Lyme Regis are well aware of the town's fragile foundations.
0:01:12 > 0:01:15Over the centuries many buildings have been lost to landslides,
0:01:15 > 0:01:20including the family home of Harry May back in 1962.
0:01:20 > 0:01:26- And what was this from here? - This was down two steps and into the dining room.
0:01:26 > 0:01:30- All meals here.- Yeah. There's not much left of it now?
0:01:30 > 0:01:32- No, there isn't. - What did it look like then?
0:01:32 > 0:01:34I have a picture of it here.
0:01:34 > 0:01:36- Which is your house?- This one here.
0:01:36 > 0:01:40Good heavens. It's absolutely beautiful, isn't it? With a balcony.
0:01:40 > 0:01:41Yes.
0:01:41 > 0:01:45Huge pagoda-style roof, looking over the bay and the Cobb.
0:01:45 > 0:01:49The building stayed upright, but in a terrible mess.
0:01:49 > 0:01:52So where did you live? Where did your parents take you?
0:01:52 > 0:01:55We couldn't move from this place.
0:01:55 > 0:02:00We have 180 degrees of sea view. It's the most spectacular place to live.
0:02:00 > 0:02:07My parents put up a mobile home in the back garden here, and then a caravan, and so it went from there.
0:02:07 > 0:02:09Gradually built things up again.
0:02:09 > 0:02:12How long have you been living in temporary accommodation yourself?
0:02:12 > 0:02:15Since 1962, always on this site.
0:02:15 > 0:02:17That's over 40 years!
0:02:17 > 0:02:19Yes, yes.
0:02:19 > 0:02:21Yes. It is.
0:02:22 > 0:02:27For 44 years, Harry has dreamed of rebuilding his house,
0:02:27 > 0:02:30but the land is simply too unstable.
0:02:31 > 0:02:37What is it that causes so many landslips in this area?
0:02:37 > 0:02:41Some answers, it seems, can be found at nearby Charmouth Beach.
0:02:41 > 0:02:44I'm meeting earth scientist Richard Edmonds
0:02:44 > 0:02:48who's been studying this coastline's subterranean secrets.
0:02:48 > 0:02:52This is the Black Ven landslide, the largest coastal landslide
0:02:52 > 0:02:55in Europe. It happened in 1958-1959.
0:02:55 > 0:02:58- This great tongue of vegetation reaching out into the channel.- Yes.
0:02:58 > 0:03:02Why is it that Lyme Regis is at such risk, Richard?
0:03:02 > 0:03:05It's built on this stuff. Its Lower Jurassic clay.
0:03:05 > 0:03:09It dates back from about 195 million years ago
0:03:09 > 0:03:10and it's very soft.
0:03:10 > 0:03:16Even worse is that the hilltops are capped with a sandstone. The sandstone is porous.
0:03:16 > 0:03:20The rainwater soaks down through it, but once it reaches these dark clays,
0:03:20 > 0:03:25it ponds up at the junction between the two rock types, lubricates the clay surface
0:03:25 > 0:03:30and great big chunks of clifftop break off and slide down the cliff face.
0:03:30 > 0:03:33It wasn't until the late 1990s that technology became available
0:03:33 > 0:03:36to offer Lyme Regis some long-term security.
0:03:38 > 0:03:42The town is now in the middle of a £24 million defence scheme -
0:03:42 > 0:03:45the first of its kind in the world.
0:03:45 > 0:03:48There are two elements. There's this massive new beach
0:03:48 > 0:03:55and then there's work in the actual hill behind the sea wall, which is prone to landslides, to stabilise it.
0:03:55 > 0:03:5875,000 tonnes of gravel have been put onto this beach.
0:03:58 > 0:04:04It's really aiming to absorb the wave energy, so the waves, rather than smash against the sea wall,
0:04:04 > 0:04:06the wave energy will be focused onto the beach.
0:04:06 > 0:04:09A second really important element is it's adding weight
0:04:09 > 0:04:12to the toe of the landslides behind here,
0:04:12 > 0:04:17so the landslides are being propped up by this massive weight of shingle.
0:04:17 > 0:04:2040 years after Harry May saw his house collapse,
0:04:20 > 0:04:22the land has been stabilised.
0:04:22 > 0:04:28Harry is now close to realising his dream of finally rebuilding his family home.
0:04:28 > 0:04:32What will you feel when you walk through the front door for the first time?
0:04:32 > 0:04:34Oh...
0:04:35 > 0:04:37Wonderful!
0:04:37 > 0:04:39Mmm, wonderful.
0:04:39 > 0:04:41Really will be.
0:04:41 > 0:04:43Very emotional.
0:04:43 > 0:04:45Mmm.
0:04:45 > 0:04:47Very.