Peter York On Ads: The rooftop community that makes plimsolls cool

Architectural fashion's a fine thing. Time was you couldn't give away a certain kind of late 1960s, early 1970s building. In the late 1980s, with period re-furb all the rage, developers would kill for a nice pompous brick or stone façade - a former insurance block with a touch of the sub-Lutyens, neo-classical would be bought, façaded and gutted, with the interior redone as pastiche with masses of mouldings. But 1960s stuff, tacky Modernism, what could you do? No bravura outside, no ceiling heights within, the whole thing was just hopeless. And in the 1990s the ceiling heights became a huge problem because there was no room to jack up the floor and lay all those cables the modern city office needed.

But, magic of magics, in the early 1990s some bright boys developing new-class city-centre flats found a way to work with those hopeless blocks, to make them chic and sleek and Modernist revival. You emphasised the structure - the steels that held the building up. You boxed up the ceiling beam and put in twinkly lights and made niches and painted everything white, not magnolia. You put some newly smart Modernist icon furniture in the show flat and the advertising and you were away. A new life for a new decade. And you could do the same for hotels. Some very unpromising buildings had a lot of value added this way. The great thing about those cheap, steel-framed blocks was their adaptability: you could cut a slug out of the middle and make an impressive atrium; public rooms made up for the smart but tiny rooms above (clever Ian Schrager pioneered this approach).

But how to love the 1960s/ 1970s buildings in big cities by major architects - different to alter and almost impossible to knock down? All that shuttered concrete stuff on the first generation South Bank in London, for instance. Idiot Sloanes always said they should come down and that they wanted to blow them down, like those famous chimneys on TV. But now Sir Denys Lasdun and his New Brutalism are fashionable and the buildings look the business. Anyone who photographs anything smart has been using them as a location for the last few years.

And now there is a new Brit commercial that's starring a building in the style. This particular building - I don't know where it is - seems to have a sort of roof-top theatre affair in shuttered concrete, an Aztec skyhouse from about 1970. It's for K-Swiss, which is kind of sports-derived footwear, what more mature people would think of as glorified plimsolls with 1970s-ish stripes and chevrons on them.

The building is an open-air theatre for skinny young, black men, a cat in a hat, a sort of fedora who does an arty little dance in his K-Swiss things - I'm not sure what generic the K-Swiss people would want you to use. Nor am I sure who they are. Are they the wonderful K Shoes of Kendal, Cumbria (the former Westmoreland) who furnished the older foot with those pre-trainer staples in tan leather with laces made by British worked in British factories? Have K been got together with some advanced Swiss types to make new orthopaedic trainers? Is Tyler Brûlé, the Swiss-loving design entrepreneur, behind it all?

There's a whole community of K-Swiss wearers up on those rooftops. There are lazy girls who just like to look at their feet. There are boys who plunge into skyline swimming pools still wearing their K-Swiss. There's a whole world up there. A community of K-Swiss wearers happy never to have to come down. Those lost boys and girls are meant to look absolutely right - the whole thing depends on it - and set off all those resonances that would make a child of 14 want to join the K-Swiss world. Is it as attractive as, say, the Levi's twisty jeans world or the iPod silhouettes world? I haven't a clue, I'm so anti sportswear-derived clothing. I'd give them all a night in the cells. But it's intensely important for K-Swiss, whoever they are, and their shareholders. (I visualise a press release that says something about cults and suggests key people own personalised K-Swisses - something about Miss Moss, perhaps, and all the Arctic Monkeys.) But meanwhile, it's all down to architecture. They've bet the shop on a stylist and a location-finder who had a thing about the Hayward Gallery.

Peter@sru.co.uk