I arrived at Terminal Five on Saturday, bracing myself. My wife and I had been in the US and we wondered if check-in would be the last time we would ever see our exchange-rate-gotten gains.

But when I say that T5 is, based on Saturday's experience, a waste of £4.3 billion, it has nothing to do with the baggage-handling chaos, which has returned this weekend. We were lucky: our luggage is safely unpacked.

Even the halfwits who run BAA should be able to work out how to move some suitcases from a plane to a carousel without losing them on the way.

The real problems with Terminal Five are far more fundamental - a design so inept that those responsible could not even build a functioning toilet.

Let's start with the hour-long wait after we'd landed before a gate could be found for the plane. Nothing new there, you say; that's long been a feature of Heathrow. Precisely. Our apologetic - and clearly embarrassed - pilot told us as we waited that there might well be an expensive new terminal but the same old problems remained.

What's the first thing many people do when they get off a plane? Go to the toilet. The genius who designed the men's loos placed the dryer at immediate right angles to the sink. So if one man is washing his hands, no one else can dry, and vice versa. Within seconds a queue builds up and the entire toilet becomes a mass of angry, frustrated and tired loo goers. The loos were, needless to say, disgusting.

But that queue is as nothing alongside that to leave the arrivals hall.

There are two working lifts to get to the car park (two more were broken). Each, with luggage, holds about five people. With no alternative exit route. And a constant flow of people trying to leave. So guess what happens? Another, far bigger and far angrier, queue. Chaos, designed into the very fabric of the terminal.

As for the design: T5's ceiling is one of those trendy affairs with all the guts showing - sort of urban metal chic (chic, that is, if it was finished, rather than with loose wires and cardboard hanging down). Mrs P, who knows about these things for a living, tells me that, if the innards are real, an expert need only study the ceiling for about ten minutes to work out how to disable the terminal. Terrorism? Who cares!

But, for all that, the single most annoying aspect of T5 is the mini-rail journey to the immigration hall. A recorded female voice tells us where we are going and what to do. In a thick foreign accent (Dutch, I think). T5 is in a British airport for a British airline. Why a foreign voice?

After using T5, it's obvious. It's in the hope that passengers will forget that Britain is responsible for this £4.3 billion farce.

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