One foot inside the new Terminal 5 at Heathrow Airport and I can sense it immediately. What IS it? Something different. Alien. Odd. Can’t quite put my finger on it. Yes, yes, there are breathtaking Grand Canyons of atriums, terraced decks laid before you like a cruise liner, a humungous roof soaring overhead, rooflights leaping like arcs of water. All very magnificent. Beneath my feet there’s an ocean of elegant tiles, sheened like a millpond, rather than that ubiquitous, standard-issue BAA carpet, speckled and multicoloured like monkey puke to, eugh, camouflage every possible hue of stain. But that’s not quite it. What IS it?

“It’s called, I hope, being treated like a human being,” laughs David Bartlett, BAA’s head of design at T5, a little nervously. That’s the devil!

Heathrow has been a Third-World experience, pretty gruelling all round. But Terminal 5? When it opens next March Bartlett can hereby confirm that you will not, repeat not, be treated like cattle. What, no cramped queue lines to herd behind? No ceilings so low they scrape your pate? No more shovelling us through with cattle-prods? No lean-to, Jerry-built sheds dressed in fag-ash rags like a student hovel? No more of that numbed panic inherent to airports, a potent cocktail of plane-missing, bag-losing anxiety — infinitely worsened by 9/11 — and ennui fostered by suspended animation in these frantic anywherelands? Not even any nonfunctioning revolving doors? Call this a British airport?

“This is a new airport building for a new age,” says Bartlett (who mostly talks in mission statements). A caring age. They’ve even put art and pastels in security to calm the nerves. “And the baggage-handling system — oh,” its architect, Mike Davis, from Rogers, Stirk, Harbour & Partners pauses, teary-eyed, as if he’s caught a glimpse of the Sistine Chapel: “A thing of beauty — awesome.”

Much of an airport’s architecture is hidden from passengers: baggage systems, all-important security systems, fuel-sup-ply systems, customs systems, the upstairs/ downstairs of services, the cafés, bars, restaurants, the comings and goings of staff, the dispensing of discounted Marlboro Lights.

“This building is 90 per cent bowels,” Davis says, “and most of us will never seem them.Drop your bag at the automatic check-in, and off it goes to the baggage halls — the size of cathedrals,” he marvels, “to be stacked by robots in storage pens before being carted off to your gate.”

Just to add to the complexity, Davis has had to disentangle his bowels on a site the size of a postage stamp — OK, the size of Hyde Park — but comparatively small, and ruthlessly hemmed in by the rest of Heathrow on one side and the green belt on the other. “Not an inch to spare,” says Davis. “We can’t go east, west, north, south, down or up, because of the planes overhead. When we dug out the foundations we had to get rid of the earth on site down the trouser leg like The Great Escape . This has been one hell of a brain ache, like a giant chess game.” And one final little pain in the neck: a ten-year public inquiry, the longest in British planning history. “I’ve been working on this thing for 19 years,” Davis sighs, “better be good, eh?”

The solution was to construct the world’s first skyscraper airport. Most airports have the freedom to sprawl — it keeps the innards simple if you can just lay them out flat. Here, though, Davis has had to entwine them through a stack of levels, “like an immense hamburger”, he adds. The trick has been keeping that all-important passenger flow one way and the other as simple as possible. Flying out, you enter and keep to the top floor, before descending on huge escalators under the tarmac to pop up into two satellite buildings. Flying in, you emerge on the escalators into the terminal and mostly keep to the lower level, before dropping into baggage reclaim and then out at ground level.

But the biggest trick has been to accomplish this technical feat and to have room at all for any architecture — public spiritedness, space, some commitment to eco-friendliness. Davis has cloaked the “hamburger” in one of high-tech architecture’s stock forms — a big tent, delicately skinned, if bulkily formed, in glass and steel a quarter of a mile (400m) long, held up with 22 giant tent pegs, joints 48 tonnes apiece, which keep the soaring roof — the largest single span in Britain — taut with the kind of calming, appropriately billowing roofspace that you expect overhead in airports but so rarely experience in Britain’s claustrophobic warrens.

Tent and burger are independentof one another, so that each level gives on to balconies with views across “canyons” all around the perimeter, crisscrossed with bridges, escalators and lifts, and on to the Berkshire countryside. There’s a lovely view of Windsor Castle.

It’s trickier for incoming passengers, who have to bore through the middle of the immense, fat building. They’ve tried to relieve claustrophobia with “intuitive” colour schemes and elegant disc lighting, but the lack of natural light tells. There’s no let-up until you break on to the bridge spanning the baggage hall, which, running the length of the building and studded with massive, soaring columns, has a heroism hitherto lacking.

Davis has squeezed every joy possible from so complex a building. As sheer architecture, though, this overcomplexity means it isn’t up there with the greats — Eero Saarinen’s TWA terminal at JFK, say, or Wilhelm Lauritzen’s Copenhagen, Norman Foster’s Stansted — “a seminal moment,” says Davis, “for generosity of space and simplicity out of complexity” — Renzo Piano’s Kansai, or even Rogers’s own Madrid Barajas, which won him the Stirling Prize last October. “It’s invidious to compare the two,” says Davis, but you can’t help it.

State-funded and less constrained, there was more room, more money for joy there than here: its roof, where most of an airport’s architecture resides, is a rippling delight, its multicoloured beams and struts as elegant as the “ladies’ ankles” that Davis wanted here. That instead Terminal 5’s are muscular and chunky is due to cost-curbing. The canyons and the pleasant pedestrian piazza that Davis has fashioned for the front — where the underground rail and Tube lines and the vast car park and bus garage converge amid trees and public art — feel rather crammed because they are. In the best airports — indeed, in Davis’s earliest, more roomy designs for Terminal 5 — the simplicity still shines through.

“This,” says Davis, “is a very British airport. Not the grand state gesture of Madrid. Each element of this had to be signed off by 43 stakeholders. Imagine! 43 stakeholders.”

This is the problemthat Terminal 5 sym-bolises. Where other countries move heaven and earth to make their modern-day national gateways into marvels, we hem ours in and, privately funded, keep a sharp eye on the books and any risk-taking. Terminal 5 has come in on time (give or take that record-breaking, ten-year public inquiry) and on budget.

This, promises Bartlett, heralds a belated new future for British airports — Norman Foster is lined up for the replacement for Terminal 2, which closes next year, Nick Grim-shaw for Stansted’s second terminal — and one which, I hope, will allow architects just a little more creative freedom, now that they have proved they can jump through the logistical hoops that Britain’s accountant culture demands of them. Terminal 5 is as good an airport building as could have been built in the conditions. Faint praise? No, the highest. It knocks spots off every other British airport except Stansted. And no speckled carpet.

Terminal 5 - the vital statistics

Length: 396m; width: 176m; height: 37m

Area: 250 hectares, equivalent to 55 football pitches

Roof span: 165m, the largest single-span structure in the UK, weighing 18,500 tonnes

Handling capacity: 36 million passengers a year

Glass façades: 30,000 m²

Car park: 4,000 spaces

Amount of earth removed: 9 million m³

Total cost: £4.4 billion

A terminal lesson on how to build the big ones

The 5,000 workers putting the finishing touches to Heathrow’s Terminal 5 need only look north to Wembley for an example of how not to run a major construction project. Wembley Stadium hosted its first public football match last month, nearly two years after it was due to open. The collapse of a roof beam caused early delays, which were then compounded by problems with sewers, subcontractors and a row with workers.

Multiplex, the construction group behind the project, then blamed the operators of the stadium. The Rolling Stones were among the casualties, as planned gigs and football matches were reorganised elsewhere. Terminal 5 started only after the longest-running planning inquiry in British history. That gave BAA the time to perfect plans and overcome problems.The construction was aided by the fact that the terminal has only one airline customer.

Jack Pringle, president of the Royal Institute of British Architects, claims that most projects that go wrong do so because of the client’s indecision. A massive building development involves a series of decisions which must be taken in strict order. Failure to do so causes delays, and delays cause other delays. “It’s all down to the organisational qualities and the decisions taken by the client. When clients know what they want, and they get the right team and take the right decisions at the right time, it all goes like clockwork.”

He points to the Emirates Stadium built for Arsenal. The club put one director on the job, and he told the architect and builder exactly what was wanted. “Decisions have to be taken on a weekly basis. You start messing around and the whole thing unravels.”

The Millennium Dome is seen as a conspicuous disaster, but Pringle points out that it was actually completed on time. “With the Dome’s structure, the client was very clear what it wanted. The project came in on time and to budget.” The problems arose when the decision had to be taken what to put inside it. The Government dithered, says Pringle. It approached a specialist agency for advice, rejected it and then went back to them 18 months later, by which time it was too late.

Dave Rogers, of the industry bible Construction News, also singles out the Emirates Stadium against Wembley. “Money is the biggest cause of rows on construction jobs,” he says. At Wembley, Multiplex, was caught out by the soaring price of steel, which could not be passed on because it was a fixed price contract.

By contrast, Terminal 5 was a “cost-plus” contract. “This means everyone gets paid.” BAA also had plenty of experience in the commissioning and building of airport terminals, he points out.

JOE BOLGER and MARTIN WALLER

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