I’ve never actually witnessed a genuine, audible gasp of surprise ripple over an audience before. But there it was on Saturday night at the Stirling Prize dinner in Liverpool the second after the envelope was ripped open and the winner announced. Gasp. Pause. And then an eruption of cheers. Low, low down on the bookies’ lists, nobody expected the Accordia housing development in Cambridge to win - least of all its architects.

"I was utterly astonished," says lead architect Keith Bradley, jaw still agape. "I was absolutely convinced Westminster Academy was going to win." He wasn’t alone. This was not only the first year that three architectural firms have won the prize - lead architects Feilden Clegg Bradley, plus excellent rising stars Macreanor Lavington and Alison Brooks Architects - this was the first year that a housing development had won, or come anywhere near. It was only the second time housing had ever been shortlisted.

Contemporary British housing has a justifiably lamentable reputation. "The last few years housebuilders have got away with absolute murder," says Bradley. And in these straitened times they’re about as popular as bankers. But here was, as the judges’ citation put it, "architecture which gives hope for us all for the future". A message, loud and clear, for the government’s communities secretary, Hazel Blears, in the audience. Accordia might not have been favourite - the shortlist was strong on "civic architecture", hinting that at last, ten years of investment in the public realm is finally paying off - but it’s a worthy winner. This is fine architecture, subtly designed and executed, and not an "icon project". Good, (pointedly) old-fashioned housing, built by a volume housebuilder, Countryside Homes, who’ve developed a reputation almost alone among their competitors for sticking their neck out.

It doesn’t take much to be radical in British mass housing. Using several architects to add variety, rather than the usual dreary, easy uniformity - indeed, using good architects at all. Quality materials. Modern design. High-ish density. Beautiful landscaping. Housing that isn’t about zooming home in your 4x4, but which nods to social aspirations. One resident interviewed for Channel 4’s Stirling Prize programme claimed to know 50 of her neighbours. This is Karl Marx to volume housebuilders. Yet here it is realised, and popular too.

But does Accordia really give "hope for the future"? No. I wish it did. But unfortunately, this is "expensive housing", as Countryside’s director Chris Crook admits. Quality costs money, a fact glossed over by both the Stirling judges and Channel 4. One newspaper suggests that this is "public housing", though only a quarter of the overall scheme can be called "affordable", let alone social housing, and that part of it is being completed by different architects and with markedly less stringent detailing. The award-winning part is high-class housing selling for between £500,000 and over £1m, at "the most exclusive address in Cambridge", says the marketing brochure. It's expensive to build, but, says Crook, "we made a profit". I ask Crook whether he’d build Accordia in anywhere other than one of the wealthiest, leafiest neighbourhoods in the country. The silence was deafening.

This doesn’t quite detract from its success. Accordia has many lessons for housebuilders, not least trusting architects and treating homeowners as more than conservative drones content with cheap finishes and Victorian-style patio lanterns. But please don’t call it a solution to British housing. Not until Gordon Brown starts nationalizing housebuilding as well as banking. As long as we rely upon volume housebuilders driven - quite rightly, as private companies - by profit, to deliver our housing, then the market will rule. And that means high-class housing for some, cruddy tin boxes for the rest.

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