Travel: This green and pleasant city

South Londoners are a canny lot. Across the unfashionable estates of Plumstead, Charlton and Wickham, for years they've kept schtum about the best walks in the capital. If you think of London as a clock face, the area between three and four contains vast swathes of quiet green spaces. Hampstead Heath, by comparison, looks like an overpopulated play area for fussy dogs and trendy liberals.

Until we saw a map of the south-east London green chain on the wall of the dentist's waiting-room, we'd never heard of Lesnes Abbey, Bostall Heath, Woodlands Farm or Maryon Park. Yet, within seven miles of the City - in SE2, SE3, and SE7 - lie parks, woods, even a farm, that make the weekend trek to the countryside along clogged-up motorways a pointless exercise.

The entire south-east London green chain runs for 40 miles between Crystal Palace and the Thames, with detours, off-shoots and add-ons. Open green areas run almost continuously, with the odd tramp through a housing estate. We weren't doing the whole 40 miles: instead we took a U-shaped eight- mile trek, from Abbey Wood to the Thames Barrier. Parked at the station (because the final part back was to be by train to pick up the car), we set off south, armed with the relevant sections of Explore, the official green chain guide.

Just five minutes into the walk, we were admiring the ruins of a 12th- century abbey against a background of steel warehouses hugging the banks of the river. The surprising quietness at Lesnes Abbey was a feature of the whole of the unknown London we discovered that day - it had a kind of end-of-the-line feel. But it could have been the totalitarian notice that put people off from lingering there for long: "No climbing on walls, metal detectors, exercising dogs off lead, taking cuttings, ball games, using radios etc, cycling, barbecues". That didn't leave much else to do, so we carried on.

Into the woods (this happened so often it got us thinking about the eponymous Sondheim musical), past the fossil beds and to Bostall, described in 1906 by a diarist as "picturesque and charming beyond description". Well, it still is, even though the trees caught the full force of the 1987 hurricane. Horizontal trunks and dense undergrowth soon gave way to open glades, where dappled sunlight filtered through beech trees and self-sufficient dogs sniffed busily at roots - and at other dogs. We met a Dobermann who snarled at us. "It's best not to move," its owner advised. "Can't you put it on a lead until we've gone?" we pleaded. "If I try to do that, he'll probably go for me," she said.

Neither of us had heard of East Wickham Open Space, a huge area where the Fanny-on-the-Hill pub - a haunt of Dick Turpin's - used to be. This part of London is hilly, like much of the walk, and there are stunning views across to the skyscrapers of the City and down into Kent.

A cluster of literary roads - Dryden, Keats, Wordsworth - led us to Woodlands Farm, with its overgrown fields, stream and run-down sheds. Until recently it was a piggery and abattoir producing bacon for the Co-op. Now, a trust is to turn it back into a working farm. For now, it is wild meadowland, ideal for our picnic. Sitting in the long grass, growing woozy on Chardonnay in the hot sun, we were deep in the countryside, with hardly a sound apart from one or two planes overhead turning in to land at City Airport. A fox watched us eating and then slunk off. We saw one person all afternoon.

Then we went across the A207, also known as Shooters Hill, notorious for highwaymen, who occasionally ended up being hanged on a spot where the police station now stands. Samuel Pepys records in 1661 riding under the "filthy remains" of a man hanging there on a gibbet. The 180-acre ancient Oxleas Wood might now be a road if locals hadn't won their campaign to save it in the early 1990s. Thank goodness they did; it has rhododendron, oak, birch, hornbeam, alder, guelder rose, midland thorn, buckthorn, dogwood, and wild cherry, along with bluebells, wood anemone, sorrel, sedges, ferns, fungi, and tree creepers, nuthatches, woodpeckers, chiffchaffs and wood warblers.

At Oxleas Wood Cafe, where we had a cappuccino overlooking the meadows, the manager, Mario, told us the area was the best-kept secret in London. "But I'm fed up with secrets," he said. "I want more people here." He showed us a cutting from the local paper in which the writer - some ghastly latter-day yuppie, by the sound of it - had complained that the cafe was "not run as cheerfully as the cafe is in the East End soap opera". He suggested it be "made more upmarket, possibly like a wine bar as you now see in Docklands".

Tucked round the back of Shooters Hill is dank Severndroog Castle, built in 1784 to commemorate Sir William James's military conquests in Malabar, "which fell to his superior valour and able conduct on the 2nd day of April 1755". It was also a lookout for spotting doodlebugs in the war. Now, graffiti declaring "Ourselves Alone" is daubed across its dripping walls.

Charlton is one of the few London areas still to have a village feel about it, not least in the fiercely loyal following of its football team. But it also has the capital's finest Jacobean house, built in 1612, with an orangery probably by Inigo Jones - which is now a public loo. Its sedate front gazes serenely over Charlton Park, where the Integrated Play Area advertises itself as "suitable for children with or without disability".

Maryon Park was the location for Michelangelo Antonioni's cult 1966 film, Blow-Up. The court where those stoned hippies played silent flowerpower tennis without a ball is still there. Above it is the hillock where the hip photographer, played by David Hemmings, unwittingly took a shot of a mysterious figure in the trees which, when blown up, linked to a suspected murder case. The paling fence by which the figure stood remains and the oak trees still rustle eerily in the wind.

Nearby Maryon Wilson Park was the scene of a daring (unfilmed) escape by two 18th-century highwaymen who tried to hide in an old drain when the entire Woolwich garrison was in pursuit. Now their hideway is a deer park and animal farm.

Gilbert's Pit, whose sand was spread over parlour floors before the days of carpets, is almost the last bit of green before the Thames. The Thames Barrier Arms has become the Barrier Animal Care Clinic and we watched anxious pet owners lugging their loved ones through the door of the old saloon bar.

Resting our weary feet on benches at the Terrace Cafe, we gazed up-river at the Millennium Dome, looked away and took another sip of tea. "It'll look OK when they take those yellow cranes away," said the waitress, on clearing away the cups.

Waiting for the train on Woolwich Dockyard station, we chatted to Charlie. "Yeah," he said, "it's always been a deprived area; that way it stays quiet."

Then, with a Cockney twinkle, he added: "There's two kinds of Londoner. Those wot live saarf of the river, and those wot would like to."

WALKING IN LONDON

WHERE TO GO

The Green Chain is part of the Capital Ring, which links 300 walks to create a circular route within a 10-mile radius of Big Ben. The 72-mile route is scheduled to be open officially by September 2001. A free leaflet about the chain is available from The London Walks Officer, Suite 425, The London Fruit Exchange, Brushfield Street, London E1 6EL.

Explore contains 10 laminated leaflets ( very useful if it starts to rain) which act as a guide and highlight sites of interest. The pack is available free from the Green Chain Project Office (tel: 0181-312 5884).

The 150-mile London Loop is due to open next year - 54 miles of it in the north are already open. The guidebook costs pounds 6 and is available from The Downlands Project, Highway House, 21 Chessington Road, Epsom KT17 1TT. (Send an A5 sae and 61p in postage.) Cheques should be made payable to Surrey County Council.

London Walking Forum (www.londonwalking.com) is putting together the capital's first complete walking guide. It will be on sale in September 2000.