You begin from Charing Cross station, London. Your train potters through places familiar from the tube map, such as Waterloo, London Bridge and New Cross, but from an unfamiliar angle - sweeping aloof past the sanctity of Southwark Cathedral and the desecration of south-east London. The pinnacle of Canary Wharf tower lingers for a dozen miles, indicating where the Jubilee Line may reach before the end of the century. Trucks toil across the Dartford River Crossing, while your train bowls across the Shorne Marsh, then dives into a three-mile tunnel to remind you what you're not missing beneath the streets of London. It emerges on the left bank of the Medway, upstream from the first stop: Tower Hill.
Tower Hill: The hill struggles to beat 100 feet in altitude, but its position means that its summit is a fine place from which to witness the cheerful confusion of the Medway Estuary. Four towns are crammed into as many miles: Chatham and Rochester vie for historical significance, while Strood and Gillingham scrap for ascendancy as the perfect dormitory town.
From Strood station, you follow the Medway downstream and soon see the wedge appear beside the waterside. Straight out of a geography textbook, it builds slowly from the west to a climax, then topples down a steep escarpment into the estuary. I clambered up the scarp slope through a miscellany of stumpy trees and bushes enlivened by some vivid wildflowers - as mauve as the Metropolitan Line, as red as the Central, and with the odd golden flash of a Circle Line buttercup.
Across the river, you can make out the keep of the Norman castle at Rochester - as high up as you are - and a brace of bridges over the Medway. No sight is stranger, though, than the one that greets you right at the top of Tower Hill.
You hear them before you see them, a rumble of diesel engines punctuated by the odd graunch of gears. Grabbing clumps of grass, you haul yourself to the lip of the summit and are startled by the sight of five bulldozers in perfect formation, flattening the already smooth earth in an unnatural arena. You have stumbled upon a Royal Engineers training ground where the military teaches civil engineering. They have to practice earthmoving somewhere, and the crest of Tower Hill is the chosen venue. At the rate they are shaving the hill, the name may soon change to Shoreditch
Warren Street: The thoroughfare that gives this Downland village its name could hardly be more different from the Warren Street in London WC1, which is a grimy sidestreet several notches less impressive even than Edgware Road and Chancery Lane.
The appeal of Warren Street, Kent, is summed up in the sign decorating the village pub, the Harrow: a ploughman, carving lazily across the North Downs - a dreamily agrarian vision beneath a benign sky. Warren Street has just enough critical mass to possess a postbox, as well as a pub, but the rewards of this metropolis lie beyond The Warren, The Gables and the contented white clapboard of Fairview Cottage. The wheat fields are full of plump, golden ears bursting to be harvested, compensating admirably for the now darkly monochrome sky. Instead of being 60 feet below the streets of London, you are 600 feet above sea level and watching the sun leak through a few gaps in the cloud, while magpies wheel and butterflies dance.
Charing Cross: Insert the letter "m" into the name Charing, and you have an instant description of this village. Half-timbered and half not, it ambles from the foot of the valley (where the railway and the A20 roar) towards the Downs. The chief attraction is the ruined Archbishop's Palace, a 15th-century manor-house which has been subsumed into a working farm.
You have a choice of no fewer than three crosses. In the churchyard, a miniature version of the Eleanor Crosses - Edward I's funerary memorials to his queen's last journey from Lincoln to Winchester. As she passed through London his memorial bestowed the name Charing Cross on what is now the hub of the capital.
Climb upwards, and swing left into a sunken lane called The Wynd, and you find yourself switchbacking to the crest of Charing Hill. The wind picks up, which is precisely why cross number two is sited here. The four sails of a handsome old windmill face squarely towards France, catching any gust that is going. The greatest cross is a long hike from here, though still within sight of the village. A vast wheat field is punctuated by a grassy rectangle. Much of the flimsy turf has been clawed away to reveal the crumbly chalk that makes up the ridge. The shape thus created is a cross, magnificent in its simplicity and its size. The White Cross on the Hill was carved out on the slope in tribute to the dead of two world wars, when Kent was the closest county to the front line. Next time you fly into Gatwick from the usual direction (the east), get a seat on the right and you can't miss the cross above Charing.
Kennington: The Kennington Loop is a legendary part of the Underground, a circle beneath London SE11 where Northern Line trains turn around for the journey back to Barnet. (Some commuters maintain that a certain proportion are lost en route, which helps to explain the dismal delays on the capital's worst tube line.) The loop around Kennington, Kent, is altogether more rewarding.
First, though, you have to find it - as tricky a job as tracking down a Mill Hill East train at Camden Town. Kennington is just north of Ashford, separated by a six-lane motorway. Even when you locate the village, the start of the Kennington circuit is blighted by ungainly housing estates whose roads mock the countryside they obliterate with names like The Pasture. (St John's Wood, on the Jubilee Line, tells a similar fib.)
As the circumnavigation continues, things improve. St Mary's Church is cut off from suburbia by some flamboyant overgrowth, and reached through an arcade of deepest green. Beyond it, Ashford cricket club plays in a more attractive arena than London's Kennington Oval; and instead of a gas-holder, the view is of an oast house or two.
You continue the loop past some fetching cottage, whose weather-beaten red turns out, on closer inspection, to be a collage of browns and dusty golds, off-whites and stray greens. Then, you emerge on to the inner circle, a massive meadow devoted to summer lazing. Idlers are provided with a carpet of buttercups, and an expansive oak or two for shade or shelter from that menacing cloud.
I came home from the nearest station, Wye. A permanent (and unstaffed) second-hand book sale is in progress there, with a box for contributions to a nearby home for the elderly. You don't find that sort of thing at Oxford Circus.