0:00:08 > 0:00:10Mist, bogs,
0:00:10 > 0:00:16no trees, no tracks, hardly a recognisable feature on the landscape.
0:00:16 > 0:00:22This is Dartmoor, the most difficult place to navigate in the whole of Britain.
0:00:22 > 0:00:26But imagine trying to cross this place without any maps.
0:00:33 > 0:00:37A few hundred years ago, that was the challenge facing an intrepid team of
0:00:37 > 0:00:42map makers who laid the foundations for today's Ordnance Survey maps.
0:00:45 > 0:00:50One of their earliest surveys took place here in Devon, and the reason for it was war.
0:00:50 > 0:00:55In 1793, France had declared war and invasion seemed imminent.
0:00:55 > 0:01:02The Army desperately needed maps to plan for the nation's defence, so who would take on a that massive task?
0:01:05 > 0:01:09Step into the breach, Lieutenant Colonel William Mudge,
0:01:09 > 0:01:12the man who would lead the Ordnance Survey to greatness.
0:01:14 > 0:01:20What I want to know is, are Mudge's maps truly accurate?
0:01:20 > 0:01:23Was defence really their only purpose?
0:01:23 > 0:01:28And can these classic maps be used to navigate across the modern British landscape?
0:01:56 > 0:01:59The first edition of the Ordnance Survey
0:01:59 > 0:02:03was the product of the most complete mapping exercise of Britain since the Tudors.
0:02:03 > 0:02:10For the first time in our history, there were maps linking county to county which covered the entire land
0:02:10 > 0:02:12based on a scale of one inch to the mile.
0:02:14 > 0:02:19The OS as we know it was the creation of Devonian William Mudge,
0:02:19 > 0:02:24who in 1791, was a 29 year-old lieutenant put in charge of this epic mapping survey.
0:02:27 > 0:02:31The end of the 18th century was a bad time for Britain.
0:02:31 > 0:02:36The American colonies had just been lost and Napoleon's forces were sweeping across Europe.
0:02:36 > 0:02:40French spies had already surveyed southern England's vulnerable beaches
0:02:40 > 0:02:46and harbours and Napoleon's fleet was on standby to attack Britain's red-coated troops.
0:02:46 > 0:02:53One unlikely landing point - Ilfracombe, on Devon's north coast.
0:02:53 > 0:02:56The story goes that the women of the town took matters into their own hands.
0:02:56 > 0:03:00Removing their red petticoats, they draped them around their shoulders
0:03:00 > 0:03:04and paraded on that hill over there and on the fields around the harbour.
0:03:04 > 0:03:08These British femme fatale hoped that by creating cliffs of crimson,
0:03:08 > 0:03:14the French Navy would think they were facing the British Redcoats. And it worked.
0:03:16 > 0:03:19The French sank a couple of Ilfracombe boats.
0:03:19 > 0:03:23But faced with what seemed to be the vanguard of the Redcoat Army,
0:03:23 > 0:03:26they thought better of landing and sailed away.
0:03:26 > 0:03:29Quite a force to be reckoned with, those Ilfracombe ladies!
0:03:31 > 0:03:36This near miss was an alarming wake-up call and so, two centuries ago,
0:03:36 > 0:03:42mapping Britain's invasion coasts became a top priority.
0:03:47 > 0:03:50I'm going to make a journey all the way across Devon
0:03:50 > 0:03:53from Ilfracombe on the north coast to Start Point on the south coast.
0:03:53 > 0:03:59I'll be following in the footsteps of Mudge's surveyors, crossing treacherous sea channels, dealing
0:03:59 > 0:04:06with a maze of lanes and confusing countryside and navigating my way across the bleak heights of Dartmoor.
0:04:06 > 0:04:10And my journey's end, Devon's invasion beaches.
0:04:22 > 0:04:25Responsibility for mapping the entire country fell to the Board of
0:04:25 > 0:04:30Ordnance, set up to supply the Army and maintain national defences.
0:04:32 > 0:04:37Their map survey began by accurately measuring a single line, then plotting two
0:04:37 > 0:04:43more lines to make a triangle, then using these three lines to be the basis for three more triangles.
0:04:43 > 0:04:47And so on. Once Mudge had created this network of huge interconnecting
0:04:47 > 0:04:51triangles, the second and third surveys filled in the grid.
0:04:51 > 0:04:55Then, after this third stage, the finer features like roads, rivers
0:04:55 > 0:04:58and bays were mapped and added to the triangulated grid.
0:05:01 > 0:05:08I'm going to follow in Mudge's footsteps by surveying the strategic Skerne Bay at Appledore.
0:05:08 > 0:05:13I'll be assisted by the Royal Engineers, whose predecessors helped on the original survey.
0:05:13 > 0:05:16We'll be using equipment from that era.
0:05:16 > 0:05:19No modern gadgets like GPS or laser sights for us.
0:05:41 > 0:05:47First, we need to establish where we are in the bigger picture in relation to one of Mudge's known trig points.
0:05:50 > 0:05:53I'm going to conduct what's called a closed traverse survey and it works like this.
0:05:53 > 0:05:58I'm standing at Appledore right here and I can see a bay curving around
0:05:58 > 0:06:01roughly like this to a headland over here.
0:06:01 > 0:06:06With the help of the Royal Engineers, I'm going to place a series of staffs
0:06:06 > 0:06:10at intervals around the edge of the bay. I'm going to measure the distances between those staffs
0:06:10 > 0:06:16and the angles between them until I get to the very end of the bay here where the headland is.
0:06:16 > 0:06:19From there, I take a final angle reading back across the bay
0:06:19 > 0:06:24to my first staff here and close the traverse. I can then draw my map.
0:06:24 > 0:06:26Let's put this theodolite together.
0:06:28 > 0:06:32Lance Corporal Anderson is dispatching his men.
0:06:32 > 0:06:37First, staff bearer John, to move from position A, to position B.
0:06:37 > 0:06:42Then, the measuring team to determine the distances between the sightingstaffs
0:06:42 > 0:06:45with an antique set of precision chains.
0:06:45 > 0:06:49If you walk along it every 10ft or so,
0:06:49 > 0:06:53there will be a marker telling you the actual distance from the end.
0:06:53 > 0:06:55But you've got to pull it tight first?
0:06:55 > 0:06:59- Yes, it's got to be mega tight.- I'm using a 200 year-old theodolite
0:06:59 > 0:07:04and the first angle I'm taking is from north round to Mudge's trig point
0:07:04 > 0:07:06at the telegraph pole on Fort Hill.
0:07:08 > 0:07:12And the reading of that...
0:07:12 > 0:07:14283.
0:07:17 > 0:07:19Now, to take our second reading.
0:07:19 > 0:07:21These first two positions are critical
0:07:21 > 0:07:26to fix and lock all our readings to fit in with Mudge's original grid.
0:07:27 > 0:07:29And that is 113.
0:07:29 > 0:07:35We've got to move the theodolite to where the staff man is on point B.
0:07:35 > 0:07:38But leaving the staff man here
0:07:38 > 0:07:43- and then we'll move John further on. - It sounds complicated, but it's dead simple really, isn't it?
0:07:43 > 0:07:46If you're not completely accurate, then nothing will tie in.
0:07:46 > 0:07:51So you've just got a load of maps that are just basically drawings. No use to man nor beast.
0:07:51 > 0:07:54- So a map becomes a drawing if you've got a mistake in it?- Yes, exactly.
0:07:57 > 0:08:00The task facing Mudge's men on the detailed survey
0:08:00 > 0:08:04to map every feature of the landscape, seems impossibly daunting.
0:08:21 > 0:08:24Finally, to close the traverse across the other side of the bay.
0:08:24 > 0:08:29This time, I turn around and measure back to where we started.
0:08:29 > 0:08:33- Is John still there? - Look at the left-hand side window
0:08:33 > 0:08:37and just come down from the left-hand side edge of that window.
0:08:37 > 0:08:38Got him.
0:08:38 > 0:08:43Final reading, back to our very first staff is 75.
0:08:43 > 0:08:47That's it. Closed a traverse.
0:08:47 > 0:08:51We've now surveyed the entire bay, double-checked the first and last positions.
0:08:51 > 0:08:53It's taken hours.
0:08:53 > 0:08:58Just imagine what it was like doing the entire coast.
0:08:58 > 0:08:59A nice cup of tea.
0:09:02 > 0:09:06The scale of Mudge's surveying achievement is mind-boggling.
0:09:06 > 0:09:13Once finished, Mudge's priority was to get the maps published and distributed as fast as possible.
0:09:17 > 0:09:19This is not a pretty map.
0:09:19 > 0:09:24It's undecorated, uncoloured and it doesn't even have a border on it.
0:09:24 > 0:09:30It's entirely a practical and totally utilitarian, functional military map.
0:09:30 > 0:09:34It's drawn to a scale of one inch to the mile.
0:09:34 > 0:09:41It's the optimum scale for the human eye to absorb a vast expanse of landscape.
0:09:41 > 0:09:45The most important thing a military man needs to know
0:09:45 > 0:09:50is the relief - the hills, valleys and after that the communications.
0:09:50 > 0:09:53The hills are very, very clearly shown by hashers.
0:09:53 > 0:09:58These hashers might look like ordinary black lines but they're not.
0:09:58 > 0:10:02They're thinner at each end and thicker in the middle. They're also wiggly.
0:10:02 > 0:10:06It's to give an impression of a hill starting on a gentle gradient,
0:10:06 > 0:10:08steepening and then flattening out on top of the hill.
0:10:08 > 0:10:12The rivers between them are very clearly marked and the river valleys, so you get an immediate
0:10:12 > 0:10:15impression of what bits of landscape are going to be easy to march across,
0:10:15 > 0:10:22where you could set an ambush, where you might expect enemy troops to approach in from the coast.
0:10:22 > 0:10:24This is primarily a road map.
0:10:24 > 0:10:29The turnpike roads are shown with a thicker black line on one side of the other.
0:10:29 > 0:10:34The ordinary country roads are shown as a pair of parallel lines, the same density of ink on both sides.
0:10:34 > 0:10:41The smallest roads of all, the unfenced ones, are shown with a very thin pecked line along each side.
0:10:41 > 0:10:44Although this is, of course, a military map, the surveyors
0:10:44 > 0:10:48who made it couldn't resist including some non-military features.
0:10:48 > 0:10:55Down here in the southern part of Dartmoor, we've got some Bronze Age hut circles here.
0:10:55 > 0:10:58An ancient cross up here.
0:10:58 > 0:11:03Down here, there's some Bronze Age barrows - it's a chink in the armour
0:11:03 > 0:11:08of this relentlessly military survey - a hint at what this map would eventually become.
0:11:10 > 0:11:15In the long run, the OS map would become the standard for military and civilian alike.
0:11:15 > 0:11:20Tomorrow, I plan to test out just how accurate the surveying team were back
0:11:20 > 0:11:25in the early 1800s, before I take on a really difficult challenge.
0:11:25 > 0:11:27Crossing Dartmoor.
0:11:45 > 0:11:47I'm climbing Codden Hill.
0:11:47 > 0:11:51It's the most dramatic viewpoint in this part of North Devon.
0:11:51 > 0:11:55It was also one of the triangulation points used by Mudge during his survey.
0:11:55 > 0:11:57It's easy to see why.
0:11:57 > 0:12:04I can see all the way south, over the Taw valley to the heights of Dartmoor, 25 miles away.
0:12:06 > 0:12:12I'm going to try and stay as close as possible to this long red straight line on Mudge's map.
0:12:12 > 0:12:17On the way, I'm going to try and locate a number of small and fairly obscure features.
0:12:17 > 0:12:21It's going to be a real test of Mudge and a real test for me.
0:12:24 > 0:12:28Before setting off, I've arranged to meet archaeologist Candy Hatherley
0:12:28 > 0:12:31to help me look for clues in interpreting Mudge's map.
0:12:31 > 0:12:34If I was going to make a journey across this map,
0:12:34 > 0:12:39and I wanted to pick up particular features marked on it which may have disappeared over the last 200 years,
0:12:39 > 0:12:42what are the kind of clues I'd be looking for?
0:12:42 > 0:12:45For structures, for example, something like a mill.
0:12:45 > 0:12:49If you went to the river, you may see a dam or a weir running to the mill.
0:12:49 > 0:12:53When you've got to the structure itself, there would be a mill or farmhouse.
0:12:53 > 0:12:57There may be stones left, the stone walls may be remaining.
0:12:57 > 0:13:01If not, there may be a lump in the ground. A piece of raised ground.
0:13:01 > 0:13:06So if you see an anomaly in the landscape, a path to nowhere, something like that,
0:13:06 > 0:13:10then you know that there could be a feature there that's disappeared.
0:13:10 > 0:13:15Potentially. Looking from the map, the map evidence shows something on site and then you go there
0:13:15 > 0:13:18and there's nothing remaining, but you have these clues.
0:13:18 > 0:13:23The evidence that's leading towards the structure that's actually no longer there on the ground.
0:13:36 > 0:13:40Mudge's map was a snapshot of the landscape of the time.
0:13:40 > 0:13:43But 200 years later, lots will have changed.
0:13:43 > 0:13:46Buildings will have crumbled, forests expanded or contracted,
0:13:46 > 0:13:51all conspiring to make my task more difficult.
0:13:51 > 0:13:55But not as difficult as Mudge's men found their part in the surveying project.
0:13:55 > 0:14:00Armed with the latest surveying equipment they stood out in the sleepy part of the country.
0:14:00 > 0:14:04They were challenged and threatened by locals who mistook them for French spies.
0:14:04 > 0:14:10Unfortunately, their outfitters had made their uniforms the same shade of blue as the French Army.
0:14:10 > 0:14:15So the surveyors were obliged to carry warrants that explained who they were and what they were doing.
0:14:17 > 0:14:21But my mission is to spot-check the features on the red line
0:14:21 > 0:14:23which crosses a track running through a wood.
0:14:23 > 0:14:28Inside the wood, the line meets a water mill which sits by a river.
0:14:34 > 0:14:39First real test of this map, and I'm not sure whether it's going to pass or not,
0:14:39 > 0:14:44is whether I can find the track running beside this small wood and field.
0:14:44 > 0:14:46The field I think I'm in right now.
0:14:46 > 0:14:48The trouble is this is a very large wood.
0:14:48 > 0:14:51It might have got much bigger over the last two centuries and I can see
0:14:51 > 0:14:54absolutely no sign whatsoever of a track.
0:14:54 > 0:14:58I think I'm going to have to take a closer look.
0:15:03 > 0:15:08Well, now I'm in this wood, things are starting to look up for the map.
0:15:08 > 0:15:11These trees are youngish conifers
0:15:11 > 0:15:13and they haven't been here for that many years.
0:15:13 > 0:15:16The wood has clearly got much, much bigger since 1809.
0:15:19 > 0:15:21This looks good.
0:15:21 > 0:15:23This is what looks like
0:15:23 > 0:15:26an old track and also the woods change.
0:15:26 > 0:15:31This is a broadleaf wood and, look at this, there's a stump here of an old broadleaf tree.
0:15:31 > 0:15:35So this is a very old wood. The trackway is very clear.
0:15:35 > 0:15:38We've got an embankment on this side.
0:15:38 > 0:15:44High bank on that side, and just over there, is the field that it should be running beside.
0:15:44 > 0:15:46And a track, so that's right.
0:15:49 > 0:15:52Now for that mill which should be near a river.
0:15:57 > 0:15:59I've been in this wood for ages.
0:15:59 > 0:16:03But I'm starting to think that I must have wandered off course.
0:16:05 > 0:16:07What's this? Look at this.
0:16:07 > 0:16:11There's a ford. This ford is on the map.
0:16:11 > 0:16:13So now I know where I am.
0:16:13 > 0:16:17So, having overshot and gone slightly off course,
0:16:17 > 0:16:20I've turned around to head back up the valley.
0:16:20 > 0:16:24If I go back up the valley and here's the mill leat,
0:16:24 > 0:16:29the mill leat should be a channel full of water that fed the mill.
0:16:29 > 0:16:35The key to finding the mill, which may not have withstood the ravages of time, is finding the leat.
0:16:35 > 0:16:38A man-made channel which would have fed it with water.
0:16:49 > 0:16:51Eureka, water.
0:16:53 > 0:16:56This might look like a woodland stream, but it isn't, it's man-made.
0:16:56 > 0:17:01It's an old canal running parallel with the contours along the hillside.
0:17:01 > 0:17:04I'll eat my umbrella if there's not a mill up there.
0:17:14 > 0:17:19I can't believe it. There's a wall crossing the mill leat here.
0:17:19 > 0:17:20Look.
0:17:24 > 0:17:28Why is that wall crossing the mill leat if it's not part of the mill?
0:17:28 > 0:17:31This part of the leat's trebled in size, it's massive.
0:17:31 > 0:17:33There's a huge pool here, or was.
0:17:33 > 0:17:36This is the mill. You can't see much now.
0:17:36 > 0:17:41It looks just like a boggy puddle, but this is definitely the mill. Just where the map said it would be.
0:17:43 > 0:17:46It doesn't do to doubt Mudge, it really doesn't.
0:17:49 > 0:17:54So, Mudge has delivered among the thickly wooded hills of North Devon.
0:17:54 > 0:17:56But tomorrow is another day.
0:17:56 > 0:18:01And a much more daunting and dangerous one for his map and for me.
0:18:01 > 0:18:08I'll be facing the ultimate test - alone on the featureless and expansive wilderness of Dartmoor.
0:18:24 > 0:18:27This is Dartmoor.
0:18:27 > 0:18:33Yesterday was a successful day for my straight line test of the map, but Dartmoor is a bleak and testing
0:18:33 > 0:18:38landscape, dotted by occasional granite outcrops called tors.
0:18:38 > 0:18:44It's a notoriously unfriendly training ground for Britain's fighting forces.
0:18:44 > 0:18:47So how well was it mapped by Mudge?
0:18:49 > 0:18:53There's something gone wrong with the map up here.
0:18:53 > 0:19:00The tor's in the right place but the moor each side doesn't correspond with the map.
0:19:00 > 0:19:05I can't believe that much is wrong, but something's not right.
0:19:05 > 0:19:08I'm going to have to go and take a closer look at the moor.
0:19:13 > 0:19:16The problem on the map is that
0:19:16 > 0:19:22it shows a stream that seems to circle the whole of High Willows, turning it into an island.
0:19:22 > 0:19:27There's no such thing of a river that goes in a full circle ahead of a river that joins its own tail.
0:19:40 > 0:19:47Well I've reached the bed of the river valley on the east side of the tor.
0:19:47 > 0:19:54Not much water to be seen, but there is a line of reeds flowing down the valley in that direction.
0:19:54 > 0:19:59You can clearly see the two slopes of the valley, just as the map says.
0:19:59 > 0:20:01No sign of water.
0:20:01 > 0:20:03I can hear water though.
0:20:05 > 0:20:07Yes, down here.
0:20:12 > 0:20:14There's water under the ground.
0:20:14 > 0:20:17I can feel it. It's quite deep water.
0:20:17 > 0:20:19Its fast-flowing. Look at that,
0:20:19 > 0:20:21flowing that way.
0:20:21 > 0:20:27So, if I follow the reeds in that direction against the flow of the water,
0:20:27 > 0:20:31with a bit of luck, I'll find out what the problem is with this map.
0:20:44 > 0:20:47I've followed the river bed for as far as I can.
0:20:47 > 0:20:50But it's just run out.
0:20:50 > 0:20:54Instead of a river, there's a great mountain of moorland in the way.
0:20:54 > 0:21:01If that river really existed, there'd have to be a 100ft deep ravine right where I'm standing. But there isn't.
0:21:01 > 0:21:04There's just this huge ridge of moorland.
0:21:04 > 0:21:11I've never, ever seen such a huge mistake on an Ordnance Survey map.
0:21:11 > 0:21:15Mudge's surveyors got it really badly wrong.
0:21:15 > 0:21:18It was hardly surprising.
0:21:18 > 0:21:24Dartmoor's landscape is riddled with bogs, peat swamps and false summits.
0:21:24 > 0:21:27On top of that, the moor can play strange tricks on the relative
0:21:27 > 0:21:33heights of large features, or where the horizon is, or even which way's up.
0:21:33 > 0:21:35Oh, and then there's the weather.
0:21:44 > 0:21:48Before I go any further, I've arranged to meet Colonel Tony Clark,
0:21:48 > 0:21:52Commandant of Okehampton Camp here on Dartmoor.
0:21:52 > 0:21:56He's trained forces personnel on the moor for over 20 years.
0:21:56 > 0:22:00So if anyone can tell me what's going on up here, it should be him.
0:22:03 > 0:22:07Why is it that Dartmoor has such a terrible reputation for navigation?
0:22:07 > 0:22:11Well when they produced this map, the points on which they did
0:22:11 > 0:22:15their surveying were quite a long distance apart.
0:22:15 > 0:22:17I think there was one over here on Cosden Beacon
0:22:17 > 0:22:21and the next one was right over here on the far side of the moor.
0:22:21 > 0:22:24So in between, the room for mathematical area was quite great.
0:22:24 > 0:22:29When they were doing the trigometrical surveys, if they found an error, they shoved it into a big
0:22:29 > 0:22:38open space and Dartmoor is mapped at a lower scale than the surrounding area because there's nothing to see.
0:22:38 > 0:22:42So this is to do with the lowest level of accuracy up here than there
0:22:42 > 0:22:45- would be for the farmland around the edge of the moor.- Absolutely right.
0:22:45 > 0:22:48The town and country planning maps are of a greater accuracy than the
0:22:48 > 0:22:51ones you get here or indeed in the Highlands of Scotland.
0:22:53 > 0:22:57How do you recommend I travel using this old map?
0:22:57 > 0:23:04Use a compass because at least if you're using a compass, you're going to be roughly on the right bearing.
0:23:04 > 0:23:06But, that's also going to give you probably the worst route.
0:23:06 > 0:23:13So, you're going to want to have your compass as a back-up and follow around the shape of the land.
0:23:13 > 0:23:16That way, you will find it by far the easiest way to get through.
0:23:16 > 0:23:22You can get into some difficulties here - the bogs, the mires as we call them.
0:23:22 > 0:23:24If your first footstep goes up to your ankle
0:23:24 > 0:23:28and your second footstep's up to your knee, then make sure your third step's backwards.
0:23:28 > 0:23:30Right. I'll remember that.
0:23:30 > 0:23:33Colonel, thank you very much. I feel cautiously optimistic.
0:23:33 > 0:23:37Any final word of advice before I set off into the murk?
0:23:37 > 0:23:40Pray.
0:23:40 > 0:23:42Thank you very much. Colonel Clarke is sure that we can
0:23:42 > 0:23:45trust the accuracy of the high points on the map.
0:23:45 > 0:23:50So I'm going to use the hilltops as markers on a route across this wasteland.
0:23:54 > 0:23:59From the summit of Dartmoor, High Willows to Lints Tor to Great Nieset
0:23:59 > 0:24:02and thence to Cranmere Pool.
0:24:04 > 0:24:07Cranmere Pool is the most remote point on Dartmoor.
0:24:12 > 0:24:17The isolation of Cranmere Pool has given it almost mythical status and as it means,
0:24:17 > 0:24:22the pool frequented by cranes, I feel particularly drawn to it.
0:24:22 > 0:24:26Let's hope that I can frequent it myself well before nightfall.
0:24:26 > 0:24:30Now, the distance from where I am now to Lints Tor is...
0:24:33 > 0:24:35..one-and-a-quarter inches,
0:24:35 > 0:24:39so at this scale of map, that makes it one-and-a-quarter miles.
0:24:39 > 0:24:45The direction is pretty much due south. So if I use my antique compass
0:24:45 > 0:24:47I can find that
0:24:47 > 0:24:49Lints Tor
0:24:49 > 0:24:55must be that black outcrop sticking up on the crest of the hill down there.
0:24:57 > 0:25:04You're not just timing yourself over a measured distance to make sure you don't overshoot, but you're also
0:25:04 > 0:25:11trying not to deviate from your bearing which means going straight through bogs like this one here.
0:25:11 > 0:25:15If the bog's too deep or wide, you can make a detour around the outside of it.
0:25:15 > 0:25:19But then you've got to somehow regain your bearing on the far side
0:25:19 > 0:25:24and the risk is that you miss your landmark at the far end.
0:25:27 > 0:25:30This is Great Niset.
0:25:30 > 0:25:33I've got nine-tenths of a mile to go to get to Cranmere Pool across
0:25:33 > 0:25:38the huge undulating, boggy plateau. Cranmere Pool's just a tiny puddle.
0:25:38 > 0:25:42My navigation's going to have to be spot on if I'm not going to get lost.
0:25:42 > 0:25:44It's going to take about 28 minutes.
0:25:44 > 0:25:48The weather's closing in, it's cold, windy and it'll be dark soon.
0:25:48 > 0:25:51I really don't want to spend a night out.
0:25:59 > 0:26:02I'm continually being
0:26:02 > 0:26:08thrown off course and so as I'm walking along, I'm trying to compute
0:26:08 > 0:26:11how many minutes to add on
0:26:11 > 0:26:15to my...the 28 minutes I'd estimated to cover the...
0:26:15 > 0:26:18nine-tenths of a mile.
0:26:23 > 0:26:26Well, my watch says...
0:26:26 > 0:26:31two and a half minutes. Well, that's so close now that I ought to start looking
0:26:31 > 0:26:33around here for Cranmere Pool.
0:26:33 > 0:26:38I think I can see a little glint of light.
0:26:38 > 0:26:40I'm hoping this might be it.
0:26:44 > 0:26:46It is.
0:26:46 > 0:26:50This, believe it or not, is Cranmere Pool.
0:26:53 > 0:26:55The pool frequented by cranes.
0:26:55 > 0:26:58It's not a lake,
0:26:58 > 0:26:59it's not even a pool.
0:26:59 > 0:27:03You couldn't even have a bath in it.
0:27:03 > 0:27:04That's Cranmere Pool.
0:27:07 > 0:27:10What an amazing place!
0:27:10 > 0:27:16Mudge's map brought me safely across this desolate landscape here to Cranmere Pool.
0:27:16 > 0:27:19Wilderness like this is almost unknown in England.
0:27:24 > 0:27:30But let's not forget that Mudge's main mission was a military one and that included our vulnerable
0:27:30 > 0:27:34invasion beaches so that we could defend ourselves from the French.
0:27:39 > 0:27:41Made it! Start Point!
0:27:41 > 0:27:45There's the English Channel, France is over there and that
0:27:45 > 0:27:52great sweeping arc of sheltered water is Start Bay, the soft underbelly of South West England.
0:27:52 > 0:27:58Start Bay has a series of the most perfect invasion beaches in the South West.
0:27:58 > 0:28:01Mudge's pioneering work meant that the British could at last
0:28:01 > 0:28:05face the threat of foreign invasion from a position of strength.
0:28:05 > 0:28:10Secure in the knowledge of finally knowing their own backyard.
0:28:10 > 0:28:17And it was only by knowing every nook and cranny of the land, that England could be defended. Thanks to Mudge.
0:28:17 > 0:28:20The French never did invade.
0:28:20 > 0:28:24Mudge's military maps went on to open up the countryside for the people.
0:28:24 > 0:28:28Our modern Ordnance Survey maps are direct descendants of Mudge's vision.
0:28:28 > 0:28:33Britain mapped in its entirety - a legacy to the nation.
0:28:38 > 0:28:42E-mail us at subtitling@bbc.co.uk