But English Heritage was well ahead of the game. They started listing post-war buildings by the mid 1980s, and this was at first deeply controversial, then gradually less so, and eventually not at all, though there is still some ritual breast-beating when another tower block is officially sanctified rather than dynamited. When they got round to listing Sir Denys Lasdun's admirable National Theatre in the early 1990s - one of the buildings previously scoffed at in a Prince Charles soundbite - it was almost possible to believe that something fundamental had changed. That the Establishment was no longer afraid of overt modernity, that the underlying mood of the country had shifted. Not so: this was not modernism pushing back the forces of heritage, as some of us had hoped, but heritage annexing modernity. It makes sense - it is nearly the 21st century, modern architecture has been around for a long time in many different forms, half the population has been born since the heyday of tower blocks - but there is something dispiriting about the process.

Although one should applaud, it never felt quite right for the National Trust to take on architect Erno Goldfinger's modernist house in Hampstead, or English Heritage to laud his Trellick Tower in Kensington. To preserve a redundant colliery such as Chatterley Whitfield in Staffordshire cannot replicate real working conditions or the real destruction of landscape that such places always caused. As for the suburbs, you could always depend on them to be monumentally unfashionable: a whole cadre of TV sitcoms was premised on this fact. Now the 'burbs are seen as unique, precious, redolent of much that is good about Britain, to be jealously cherished.

The warm embrace of heritage removes the necessary distinction between what is modern and what is not. It is not just that "modern" things are getting old: it is that the dogs of heritage, in their excited scent-marking activities, have come charging right up to the present and into the future. It used to take about 50 or 60 years for a building to be deemed historically important, then 30 years, then 15 (a Norman Foster building was listed at that age). Today, English Heritage has turned the whole thing round and likes to comment on buildings yet to come - for instance in its enthusiastic support for Daniel Libeskind's still-unbuilt "spiral" extension to the Victoria and Albert Museum in London.

Call me old-fashioned, but I liked things better when you knew which side people were on. When perplexing new architecture was in one box and Stonehenge was in another, and you knew which was which. When Richard Rogers was a radical, not a Lord. This proves that I am as guilty of nostalgia as anyone. For part of me likes the heritage process. I would fight to have Rogers' Lloyd's of London building listed, were it threatened, for what it and he once represented. I would like to see Gateshead's Brutalist multi-storey car park - the one with the empty nightclub on top, as immortalised by Michael Caine in Get Carter - preserved as a filmic reference. But if Rover's Longbridge plant, for instance, closed, would English Heritage pounce on it, and issue calls for it to become a museum of the British car industry? Let us hope not. Nor should it be cleared away to build estates of Noddy housing. It should remain, hundreds of acres of it, as a derelict, dangerous memorial behind miles of barbed wire. That way, we'll really know what we've lost. But that is the one outcome that will never be allowed to happen.