This demi-paradise: Martin Plimmer lets fly at Heathrow Airport

Why is it everybody at Heathrow looks so glum when most of them are on holiday or about to meet relatives from Canada? Well, for one thing, they've seen too many tie shops and are feeling queasy. And they've passed through so many Hounslows on the Tube journey that they want to go home. But the main reason for their gloom is that Heathrow is such a bloody awful place. It was built in the Forties by far-sighted people anticipating Small is Beautiful. Since then, it has swollen grossly, with new structures squeezed on top of, underneath, and behind the toilets of what was already there. The result is a Lego heap of gloomy halls and temporary buildings, often shrouded in scaffolding, connected by confusing home-made ramps, whose wooden creakings and sighings evoke the era of tall ships.

My best advice, given with the wisdom of experience, is not to check in at Terminal 2 with your family five minutes before your sunshine plane is due to leave Terminal 3. Signs to Terminal 3 lead you scrambling down a long ramp and on to the street to a shed marked Building B136F and a sign which says: "The compactor is now located in the forecourt at the front of Terminal 2 Office Block". You may as well kiss the sunshine goodbye.

This, give or take O'Hare, Chicago, is the most important airport in the world. If the 49 people who were expected to pass through Heathrow in its first year of operation were the only ones who used it today, they would find themselves with a tie shop each. But now there are 44 million other passengers, and they simply don't fit in. The check-ins at Terminal 2 have been squeezed into an area that in Mission Impossible would be reserved for service ducting and unbelievable escapes. The ceiling here is lower than the ceiling of the smallest room in my house. I'm not bragging, just stooping.

Does any of this really matter? After all, few people go to Heathrow to go to Heathrow. They go to Heathrow to go to somewhere else. It's a cosmopolitan ghost-town full of fluttering transient souls. Pity those damned to spend eternities here: Sock Shop Sheilas, foreign menials with mops, the jet-lagged and plane-less, in impulsive jazz-patterned ties. And the British Airport Authority walkie-talkie men, who walk round in small circles looking at the floor or the ceiling, like people talking into walkie-talkies do. "Look Frank, I'm at ramp six, car park 1a... Where's Terminal 3 again?"

Yes, it does matter. Go to Stansted and you step into the future. This is an airport with a capital AIR. Heathrow does nothing to amaze its customers. It fobs them off with Food Village. It isn't a village; it's the most important airport in the world. It should look the part. We built the best parts of Concorde, yet we still haven't quite cracked the airport trolley. The Swiss have trolleys that go up escalators and round corners. Previous Heathrow trolleys only moved if you squeezed the handle. The current design stops if you squeeze the handle. The difference is that if, like the pyramid builder, you momentarily let go to consult your compass at the top of one of Heathrow's many ramps, you might take out a gaggle of Canadian relatives. Nobody wants to die in a loud tie, not even a Canadian