A medieval outline of Britain lurks beneath the glass of Terry Jones's coffee table. In the first of a series on the fascination of maps, the former Python comedian explains his obsession
"YOU can see it's England," says Terry Jones. "To me it's miracle how they did it. There were no satellite pictures."

Not in 1360, there weren't, the approximate date of the "Gough Map", Britain's first road atlas. Scotland is more impressionistic, with a rectanglar shape and a here-be-dragons feel to it - and no wonder: "England was at war with Scotland when this was made," says Jones, the former Python who recently presented the BBC2 series on an earlier set of wars, Crusades.

Wales is on the large side and Cardigan Bay is missing. The Cornish peninsula has been slightly squeezed. But the medieval cartographer deserves full marks for ground-breaking work in drawing the Isle of Wight so that you can recognise it. Previous cartographers had thought of England as an oval only slightly larger than Wales or imagined that the east and south coasts were in one straight line. Dating back to the end of the Black Death, this work - about 16 inches to the mile - is the earliest surviving map to depict Britain with any accuracy.

"It is unique," according to E J S Parsons, the author of the explanatory leaflet for the Bodleian, the Oxford library which inherited the map in 1809 from a collector named Richard Gough.

The original is priceless but the Bodleian sells copies at £12.95. Jones bought his copy 15 years ago, when, the last of the Monty Python tele- vision series behind him, he was working on something completely different, a book on Geoffrey Chaucer. "1360 was exactly my period. It was interesting to know what concept of the world people had."

Like the original, the copy is almost 4ft by 2ft and comes in two sheets. Jones stuck them together, placed them between two panes of strengthened glass, added legs and thus acquired a coffee table.

"I do like maps; I must say that I've got a touch of cartophilia," he admits, shifting the teapot to give a better view of the Insula de Man. He is doing pretty well for maps ancient and modern. The 1991 Ordnance Survey motoring atlas sticks out of a shelf near the cartographic coffee table. Another Ordnance Survey map, dating back to 1916, shows that his part of south London was crammed with "picture theatres", "lunatic asylums" and lavatories.

Less useful, but more intriguing, is Paterson's Roads, a publication covering the "Direct and Principal" routes of the 1840s. It isn't an atlas but a list of points of interest on specific routes, including the names of the more respectable residents, which makes it a kind of telephone directory without phone numbers. "Maybe you were supposed to call on them," suggests Jones.

He also has a copy of Ogilby's Britannia, a road map which illustrates a number of set routes by showing only the highway itself, indicating the position of junctions, inns and - crucial to horse-powered travellers of 1675 - the uphill bits. The book of the TV series (Crusades by Terry Jones and Alan Ereira, BBC Books, £17.99) includes an earlier version on the same minimalist principle, depicting the route between London and Jerusalem.

The Gough map, though, is the complete works, including the major thoroughfares out of London, the rivers and a few helpful remarks in Latin. Sutherland bears the warning, "Here be wolves". More contentiously," Trojans landed" in Devon. Legendary shipwrecks also feature. Fishes the size of the Isle of Wight decorate the sea. The sea beyond the north of England is labelled Mare aquilonare sine termino, or "Sea of the north wind without end" - though it does end, in the Danish coast. Also marked for the benefit of really intrepid travellers are the east coast of Ireland, with "Develyn" or Dublin, and "Caleys" or Calais, complete with a sort of logo.

Instead of having north at the top, the map follows the medieval Christian tradition and is tilted through 90 degrees so that we are looking east. To read the place names, which are written north-south instead of along the east-west axis, Jones has to position himself behind Wales on one of the long sides of the coffee table.

To judge by rusty holes around the edges on the original parchment, this offical piece of cartography must have been nailed to a board or wall. Many of the names were rubbed off at the lower, ie western, edge, by the sleeves of the couriers, courtiers and others consulting the map. Good memories were needed. Since there were few - if any - copies, no one could take it on their journeys.

As one of the few charts to the hinterland of Britain, it must have seemed a wondrous production. Jones is still impressed by this 600-year-old creation: "Everything was done on foot - or by boat: they've made the rivers wide, being more important than roads."

Over the centuries it became obsolete and ended up as Lot 405 (it still bears the number) in an auction on 20 May 1774, where it was knocked down to Gough for half-a-crown (1212p nowadays, but worth a good bit more in the 18th century). It was part of his magnificent cartographical collection which he passed on to the Bodleian and hence the nation at his death. Maybe Terry Jones will do the same with his copy. "The Jones Coffee Table" could occupy pride of place in his local library.

Jonathan Sale