This boils down to six four-storey, roughly U-shaped buildings placed in two rows back-to-back - though the impression is of a tight cluster of more than a dozen separate pieces. This is because the arms of the buildings, each differently curved and angled and with a variety of little pavilions and other add-ons, make courtyards stretching out into the landscape. The central gap between the two rows is glazed over and turned into the street, running from end to end. Torp and Neslein then vary all the different bits of buildings within an overall hierarchy of around six different basic shapes and just two surface treatments: stone or grey-painted metal. The result is a place that seems haphazard but which is very tightly controlled.

If you half-close your eyes and look at the plan, it starts to look a bit like a fish skeleton. The head is the reception, the spine is the street, the curving bones are the wings, the tail is a spreading arrangement of cafes and restaurants set on the lake. None of this is immediately apparent, however, when you get off one of the white BA staff buses that perpetually encircle Heathrow. Waterside, which you arrive at end-on, at first appears to be almost disappointingly modest. There's a nice hummocky green landscape with lots of trees and water, a forecourt with a gurgling fountain, a glass entrance canopy between sharply-angled low limestone-clad office wings, little else. Oddly, you're not even particularly aware of planes, since the site sidesteps the flightpath. This could be any half-decent business park, anywhere. But once you're through the doors, you're in a strangely different world.

A stream bubbles along the floor of granite setts. Street-like things such as lamp standards and trees are much in evidence. There are cafes, a little Waitrose food store, a newsagent, bank, a hairdresser, a library, art gallery and so on. In the middle it widens out into an arena-like town square (Torp wanted a tower here to act as the "church", but the planners wouldn't allow it). In the wrong hands, such a place could only too easily be just another kitsch shopping mall. But here virtually everything is coolly Nordic. Neslein, flying in to check on progress, is outraged at little unauthorized outcrops of bad taste like a market barrow for a flower stall, and sundry garish soft drinks-vending machines. On his tour round, he takes the guilty people aside to remonstrate with them. But he shouldn't worry. What other shopping mall has big bits of aircraft undercarriage, and a 1960s Bedford BOAC van, acting as sculpture?

It must still be a bit unnerving for the old-style BA managers to see their staff having what appears to be a permanent lunchbreak. Mobile phones and laptop computers are much in evidence at the various (non-alcoholic) watering-holes along the street. When you venture into the office wings (each gently themed, like the tailfin art, on a region of the world), they seem half deserted. No wonder: as soon as you downgrade the importance of the desk, people are going to go walkabout. BA's project director Chris Byron is however sanguine about this. Out in the street, people meet each other more, he reflects (we are talking in a café, naturally, rather than his office, assuming he has one). People, you can't help noticing, spend a lot of time asking other people where a third person might be found.

By the time I'd got to the glass "show-and-tell" cabinets at the entrance to each office section, having seen the communal computer/video screens that people gather round, and the little relaxing areas and the contemplative olive-grove - I'd realized what this place reminded me of. It's the world's biggest nursery school. Various manager/teachers benignly keep half an eye on their charges as they romp around the place. Bob Ayling's room near the hub of things serves very well as the head's office. Where in a nursery you find communal boxes with rows of scissors or paintbrushes, here you find the same thing, only offering mobile phones for the day. Work and play are indistinguishable, or seem to be. It looks as if everyone is one big happy family.

And just like a good nursery school, someone, somewhere, is making a note of your work and gauging the results. Even smiley nursery teachers have reports to write and school inspectors to face. For all the hang-loose feel of Niels Torp's Waterside HQ for BA, it is quite clearly a devilishly hard-edged people-processing machine. So they're happy there? So they work harder. Why else would BA, or any other world-class company with shreholders to please, build such a place? This is not architecture, in the end. It is social engineering.