Not so long ago, there was a lengthy debate over whether James Stirling's notoriously trouble-prone 1960s history faculty at Cambridge University should be demolished. What with leaks, and the fact that you sweated in summer and shivered in winter beneath its great glass roof - plus the fact that it was inclined to shed its red-tiled skin - it seemed scarcely worth keeping. Yet it was kept, and mended, and now enjoys iconic status. An earlier trouble-prone building by Stirling with James Gowan, Leicester University's 1963 engineering department, took a lot of expensive fixing - and is now a listed building. As is the National Theatre, once famed for its leaks.

We can be sure, then, of one thing with today's crop of problematic avant-garde architecture. Broken glass will be replaced, rusting pipes will be fixed, perhaps some design changes made. But the heritage police will be on the alert. If Rogers' 1986 Lloyd's of London building were threatened with seriously insensitive alterations today, English Heritage would swoop and spot-list it in a trice. Sir John Soane, by the way, worked for free at Dulwich. Perhaps they should have paid him.

From William Golding's The Spire