The Stade de France is, as it happens, a bit of a Blairist enterprise. In the past such magnificent bits of French civic architecture would have been wholly paid for by the state, without question. Not any more: the coffers have been depleted by the effort to cut public spending so as to meet the criteria for the Single European Currency. So the stadium was built in less than three years by a 47:53 public:private sector partnership, at a cost of around £260 million. The private operators will take the profits for 30 years, after which the stadium will revert to the City of Paris. Macary and his partner Aymeric Zublena form half of the architectural consortium (Macary-Zublena/Regembal-Costantini) that designed the Stade. They are insistent that this was a marvellous way to fund the place. "Otherwise," says Zublena, "It would have been years before it got built."

This is the first stadium they have ever designed: they won the three-stage competition in April 1995, finally beating Jean Nouvel in a head-to-head. As is the way in France, the final decision was down to the personal choice of a statesman - in this case the outgoing prime minister, Edouard Balladur. With only three years to go before the World Cup, that was cutting things a bit fine. Yet the Stade opened in January on what was previously a derelict gasworks in the northern suburb of St. Denis. Not only the stadium but also two new stations to serve it, one each side, on different branches of the RER express commuter network. In the months that followed they finished off all the new roads, landscaping and so forth. The stadium is already much used, not least by three local teams. You just can't help but be impressed by the massive efficiency of the effort.

The Stade incorporates two big ideas. The first of these makes it a landmark of northern Paris: the roof. Usually stadium roofs follow the shape of the stands below: oval or rectangular depending on the layout of the seating, flat or undulating depending on whether the seating is regular all round, or stacked up higher at the sides - which spectators prefer. Here, the seating rises at the sides in the approved modern manner, but the oval roof is kept flat by being set up high on suspension masts, floating like a giant Frisbee. Being wholly detached from the stands in this way, it is free to project outwards as well as inwards, so giving some shelter to people arriving at the gates all round. This immense disc is floodlit from beneath, glowing like a Spielbergian mother ship. It is a brilliantly simple visual trick - though I've no idea how well it shelters people in driving wind and rain. Zublena points out the perforated metal windbreaks at the back of the stands, but that's not quite the same as enclosure, is it? After all, the canopy has to be held down with tension rods round the perimeter to make sure it doesn't blow away.