Stuck in an aerial traffic jam high above central London, even the most jaded international executive gawps at the miasmic, jewel-encrusted city spread out beneath the circling plane.

If only the windows of jumbos and Airbuses were bigger; seatbelts strain and necks ache as Heathrow-bound passengers struggle for the best views of Big Ben and Buckingham Palace or try to spot their home, wishing they could parachute down into the back garden rather than sweat out the persecution of landing, immigration, luggage carousel, customs and the stop-go Underground.

For those few minutes, London, on a clear day, appears a city of promises and dreams. It seems a pity that, from your seat in a descending airliner, you see it as if through the wrong end of a telescope, tantalising, but so far away.

To get closer, to see London from pigeon perspective, you need to fly in a light aircraft, airship or helicopter.

In recent years, this privilege has been offered only to the few. Not only

is flying a private plane an expensive way of stirring the A-Z into three dimensional relief, but the air controllers at Heathrow are not especially keen on Pipers and Cessnas buzzing their leisurely way through impatient swarms of Boeings, Fokkers and Iluyshins.

This is where London Scenic Flights buzzes into the picture. Less than a month old, but using tried and tested planes and pilots, this tourist-oriented outfit offers 30-minute flights across central London. It picks up passengers from any hotel in the city centre and chauffeurs them to Stapleford in Hertfordshire (a

50-minute drive from the centre on a normal weekday).

Ready and waiting to go at Stapleford, between fields of horses and cows, Mock Tudor pubs and the M25, is a twin-engined Piper Seneca and a natty pilot with a firm handshake capped with a relaxed smile. Clamber across the wing, strap yourself in, and the waspish plane is bumping across the airfield. Before anyone has time to bottle out, the pilot boosts the engines up to 2,500rpm, eases off the brakes and sends the four-seater wobbling along the turf and up into the hazy August sky.

At 700ft, the city climbs over the horizon, at 800ft the Thames flashes fire as it snakes into view. At 1,500ft, the pilot levels out and, following the M25, heads for the river, turning west over the brutal Queen Elizabeth Bridge.

From here the Thames draws us over the twin cities of London and Westminster: this is the route followed by unwelcome German tourists 50 years ago as they flew to Docklands and the City by Heinkel 111, Dornier Do-17 and Junkers 88.

This was where famous propaganda pictures of Gott strafing England were taken by one Luftwaffe bomber flying leap-frog above another and snapping it in action. And this is why on your left and right there are so many Fifties' tower blocks pointing accusing concrete fingers into the smog-fringed sky.

Until the plane reaches Gotham City E14 (aka Canary Wharf), the Thames still bustles. Here are dredgers and barges, police boats in a flurry and freighters paying a call at Ford's mighty Dagenham works.

At Canary Wharf, City Airport begs attention. Can international jets really take off and land on a runway that seems no longer than a cricket pitch? We have a second look as the pilot circles the stainless steel monolith we call Canary Wharf Tower. We are flying 700ft above its pyramidical roof. If this was the Empire State Building, we could reach out and touch the tip of its spire. For all its notorious tower blocks, London is not a tall city.

The Isle of Dogs surprises with a generous sward of green at its heart, while the Thames tricks and deceives the eye as it places and relocates Tower Bridge, the Tower of London, St Paul's, the gleaming carapace of Waterloo International station and the Houses of Parliament. You only finally get to grips with the serpentine twists and turns of the Thames from the air.

The A-Z might tell you something different, yet it is hard not to expect London's most famous monuments to pop up in linear succession. From 1,500ft they refuse to co-operate. You must lean now to the left of the little plane, now to the right as Big Ben rears up where you least expected it to do so. Look over there and the British Museum is playing the same trick.

From these antics, you learn that London is no axial city. This is not Paris, much less New York. Save for The Mall, there are few grand avenues and arrow-straight roads. The metropolis corkscrews like a City dealer lit up for the night trying to negotiate his way to Liverpool Street station and home. You also learn that the historic centre of London - tourist London - is surprisingly small, while all around the slop of inner and outer suburbs washes in muddy waves as far as the eye can see. How tiny St Paul's looks surrounded by the commercial might of the modern city; how lost the towers and spires of Wren and Hawksmoor churches.

As the plane banks over Vauxhall Bridge and the Tate Gallery at the beginning of its homeward run, London yields other surprises. There are great courtyards hidden from public view at Buckingham Palace, St James's Palace, the British Museum and the Palace of Westminster. There are astonishing roofscapes (although Londoners make precious little use of their roofs which are, for the most part, terrace free) and gardens, gardens everywhere.

Within minutes of heading east back along the river, the greenness of London is as remarkable as it is effusive. There is the police shooting range at Rainham, the marshlands out Erith way, the remains of cockney forests and the football fields of Hackney Marshes. You simply cannot see this from the confines of a car fuming its futile way around the North Circular.

Sadly, your mastery of the geography of London lasts little more than half an hour. When the Piper drops to 600ft on 'base leg' as it prepares to land back at Stapleford, you can see the next party waiting to experience this heavenly conjuring trick. The pilot with the firm handshake and reassuring smile drops the plane

neatly on the grass runway and we are back to earth, the M11 and a strangling by summer smog.

Back on the ground, you want to go up again. Imagine hanging upside down in an open cockpit Tiger Moth and seeing tall buildings looming like stalagmites above, or flying sideways on so that you can peer into the narrowest City alley, seeking out such hidden gems as St Mary-at-Hill and the cunning skylights of Sir John Soane's Museum in Lincoln's Inn Fields.

There is sorcery in low-level flight. It transforms the city you curse into a new-found land. Try it at least once, or be forever condemned to twisting your neck in a jumbo jet.

London Scenic Flights (081-896 3066): pounds 99 per person; family ticket (up to two adults and three children or one adult and four children), pounds 299; Children under 14, pounds 69; children under two, free.

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