There is a difference between the kind of architectural commissioning that sees architects primarily as set designers - and here the enlightened Vittorio Radice of Selfridges deserves applause for his shrewdness in relating fashionable progressive architects such as Future Systems and David Adjaye to fashionable retailing - and the kind that serves to advance the art and science of architecture. There have always been fashions in architecture, and clients desperate to "get the look", whatever it is, but it's a risky business because getting anything built takes so long that it is generally outmoded well before it finally appears on the street. A store fit-out such as the Manchester Selfridges, for all its huge cost, can be ripped out and re-done at speed. A complete sizeable public building takes rather longer.

Which is why Foster's Swiss Re building in the City - not so much a gherkin as an upturned Zeppelin - stands out in more ways than one. A model of it is on display at the Venice Biennale, and it provides a moment of calm assurance. It is of our time. It is not a fashion statement. Some other recent products of the Foster stable - whether the ludicrously over-wrought London City Hall, or the desperately dull HSBC tower at Canary Wharf - do not enhance his CV. The 40-storey Zeppelin, however, most certainly will. The Right Angle Club ought to disapprove - and its members note that French superstar architect Jean Nouvel is planning a remarkably similar equivalent in Barcelona - but the fact remains that there is a logic and consistency and a satisfying inevitability to the Zeppelin. Its shape, tapering towards the base, allows for public open space in the overcrowded city. Its slippery form means that the wind will not blow you off your feet nearby on windy days. Lightwells(originally planned as planted atria, but somewhat reduced) spiral round the perimeter. That shape helps it to be low-energy, using the wind for ventilation and maximizing daylight in the offices.