The conservationists should have held their horses. What Sir Norman produced at the academy in Piccadilly, London, was a small masterpiece of sensitive modern intervention. The Royal Academy is a better place for the Foster-designed Sackler Galleries and the new work has been acclaimed internationally by curators, architectural critics, the visiting public - and even conservationists, including Alan Powers, secretary of the Twentieth Century Society.
What matters most when remodelling an old building is the ability, imagination and sensitivity of the architects and not whether they can promise to restore exactly what was there before in slavish detail. This approach - sensitive intervention while restoring - can also be seen to advantage in such buildings as the Castelvecchio museum in Verona (rebuilt by the Venetian architect Carlo Scarpa in the Sixties) and the newly rebuilt King John's Castle, Limerick, by the Dublin architects Murray O'Laorie.
What Sir Norman did was to reveal the fact that the Royal Academy is not one building but two, separated by a 14ft gap. Working with Julian Harrap, the conservation architect, Foster restored and revealed the walls of the two buildings (one Georgian, by Samuel Ware, the other Victorian, by Sidney Smirke). Between the two walls he created a magnificent stairway and glass lift rising to the Sackler Galleries. Far from demeaning the academy, Sir Norman's design has enhanced it.
Is this sufficient proof that an ultra-Modern architect such as Sir Norman can be trusted to work on a sensitive listed building? 'The Royal Academy is not the same thing as the Cohen house,' says Mr Powers. 'At the academy, Foster was filling in a blank hole; at Old Church Street, Mendelsohn has already filled in the hole perfectly well. Foster's design at the academy is very good, but it hardly bears comparison with the situation in Chelsea.' One thing is for sure: Sir Norman Foster - in so many ways an unlikely candidate - is at the centre of the latest conservation debate.
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