From the remote Stone Age mounds and standing stones of the Orkneys to the well-trodden turf at Land's End and from the fens of East Anglia to the wild mountains of Wales ''David Gentleman's Britain'' reveals the landscape and architecture of the British Isles. His techniques, watercolour and pen and wash, are familiar and traditional but his approach is startlingly individual and vigorous- both in his drawings and in the text that accompanies them. Cotswold villages and city suburbs, country lanes and motorways, beauty spots and black spots, landmarks and follies of all ages are contrasted to produce a matchless and magnificent rendering of Britain's landscape.