Last Saturday, I left the ghost of William Cobbett, the 19th-century rural radical, at old friends in Gloucestershire. We came back to The Wen, as he called London, by different paths, he in the saddle, I at the wheel of an XKR Jag. Both of us had seen the English countryside changing before our eyes. Land continues to be enclosed, or privatised. Suburbia seems to have spread along with baseball caps, burgers, PFI (private finance, ie junk) architecture and leisurewear across the home counties. Yet, despite such development, doesn't England still look green and pleasant from the windows of Gatwick and Heathrow-bound airliners?

Perhaps I could entice the spirit of Cobbett to check the situation from an aerial perspective. I'm not sure what Cobbett would have made of a Rural Flight. He probably thought hot air balloons, pioneered even before his time by the Montgolfier brothers in Paris, "execrable" and "villainous". So, with trepidation, I imagined him clambering aboard a plywood and canvas Tiger Moth and taking him up over the South Downs to follow parts of the rural ride he made from Worth to the Kent coast.

We take off - well, I do - from a friend's landing strip not far from Shoreham, the biplane's 130 winged horses lifting us at 700ft a minute above the South Downs and Ditchling Beacon. I imagine Cobbett leaning out of the front seat and stabbing a broad finger towards the showy tax-eaters' houses of Brighton down below. Brighton, of course, is as fashionable today as it was in the 1820s when King George IV played there in his more-than-showy Hindoo-Chinese Pavilion.

There are fewer sheep than there used to be on the downs, yet the country remains surprisingly delightful as these give way to the Vale of Kent. Cobbett leans out to see the stables at Plumpton racecourse. There are no motorways and few obvious man-made markers along our route, although I spot a plume of steam from a train on the Bluebell Railway between Sheffield Park and Horsted Keynes at nine o'clock; Cobbett recognises Tunbridge Wells and is disgusted by the tax-eaters' villas that surround it. He indicates the road he took from his original starting point at Worth, to our west, but I keep on a north-easterly course for a few minutes more to reveal the Farm Museum at Henhurst. The country, I say above the steady thrum of the four-cylinder engine, is increasingly in hock to museum culture.

I turn the plane quite on its side to bring us over Rabbit's Cross. This is only because I like the name. No amount of unsympathetic rural development can rob the English countryside of its lovely litany of names. I can't help wondering who the rabbit was and what had upset him. I turn again over Hareplain. Cobbett loved hunting hares and I love airplanes. Then it's down over Vita Sackville-West and Duncan Grant's Sissinghurst, Tenterden and Appledore to Romney Marsh.

As the Channel heaves into view, I feel the the airframe shaking. Cobbett is working himself into a rant. No, it's not that he's remembering the Methodist meeting house he visited at Goudhurst where he had never heard such "whining cant" and "foppish affectation" before. It's not even the sight of the politically corrupt "rotten borough" of New Romney, but that of the Martello towers that line the shingle beaches here and were built to keep Napoleon at bay; these and the Royal Military canal, a long, thin silver mirror along the 30 miles from Rye to Hythe. The Martello towers, says Cobbett, are a squandering of public money. As for the military waterworks, were "those armies who had so often crossed the Rhine and the Danube to be kept back by a canal, made by Pitt, thirty feet wide at the most!" Even so, they might have come in handy a century on from Rural Rides if Hitler had launched Operation Sea Lion and invaded England.

I point to well-drained fields of Romney Marsh sheep, which calms Cobbett, who admires these "very pretty and large animals". And then I find myself ranting as we buzz over St Mary in the Marsh. This much-loved church is now faced by a horrid estate of executive housing more suited to Swindon than Romney Marsh. The suburbanisation of the countryside has even reached this remote corner. And then the landscape opens up to a world of timber cabins, ancient railway carriages turned into homes, fishing boats tied to the beach by chains, the miniature main-line steam trains of the Romney, Hythe and Dymchurch Railway that, implausibly and magically, take schoolchildren to New Romney compre hensive, a lighthouse, a nuclear power station and Derek Jarman's favourite sausage-and-chips cafe at Dungeness station.

Ragamuffin settlements such as Dungeness are rare today. A rural home in the country seems almost out of the question unless it's a part of some housebuilder's cul-de-sac. Cobbett, by the way, was fond of Gypsies (I tell him our machine is powered by a Gypsy Major engine), a defender of witches and poachers, too. Unfashionably, he championed Irish refugees in England even before the potato famines of the 1840s. Hated potatoes, though; these were brought into England by "one of the greatest villains upon earth" (Sir Walter Raleigh). Cobbett thinks it a pity that Raleigh wasn't executed before he imported this execrable root.

Beneath the bluster, Cobbett is on the side of the angels. We turn and climb up away from the suburbanised south coast to Angels five (5,000ft). At this height, the sky whitens. I screw up my eyes and the rural champion vanishes. I had planned to give him a lift back to Worth, where he set out on his Rural Ride to Kent in August 1823. But as Worth is now a part of Crawley new town and on the flight path to Gatwick airport, an enclosure of air, I sideslip down on to my pal's buttercup-laced field, and drive back by Jag to The Wen. I shall miss Old Cobbett.

• A new edition of Cobbett's book is published by Penguin on September 27. To order a copy in advance call 0870 066 7979