When is a building a work of art?

If property is theft, as Proudhon had it, architecture is a steal. In the British government's mind at least, architecture (and particularly architecture in the public realm) is something to be plundered and sold whenever the Treasury coffers need a boost or ministers are unable to think of intelligent new uses for old buildings.

Over the past few months one minister, more so than most, has found that the inability to distinguish property from architecture has cost him surprisingly dear. That minister is Michael Portillo, although he has been run a close second by Virginia Bottomley, Secretary of State for National Heritage.

For Portillo (and presumably his advisers) there is no material, nor aesthetic, difference between a second-rate Sixties office block and Admiralty Arch, or between a half-decent Fifties office building and the Royal Naval College, Greenwich. All are properties that need clearing from Whitehall decks and flogging off to private enterprise.

The reason a senior Admiral called Mr Portillo a "little creep" earlier this month when the Secretary of State for Defence tried to off-load Admiralty Arch was less because of the intrinsic architectural worth of this starchy Edwardian edifice and much more because the minister had the affront to put his hands on one of the senior service's most prominent assets.

Over Greenwich, however, Mr Portillo came a cropper. Not only has the attempt to sell off some of the greatest of all Renaissance buildings been seen as a low and tacky move, but, at the end of what has been a long day for Mr Portillo and Mrs Bottomley, only eight offers for the Royal Naval College have been received, and of these (the bid from the University of Greenwich is the exception), seven have been not much more than half-baked. While this is not surprising given the foreshortened time scale dictated by the Ministries of Defence and National Heritage, the Government must have learnt that the sale of great architecture is both unpopular and problematical.

The mud from the Greenwich sale (and to a lesser extent that of Admiralty Arch) has stuck to Mr Portillo's coat-tails. Whatever high or low places he moves to in years to come, he will be remembered as the politician who tried to sell Greenwich and couldn't tell his architecture from his elbow.

This inability to distinguish run-of-the-mill bricks and mortar from works of art is a distinguishing feature of British governments (pace Michael Portillo) and, indeed, of many British businesses.

Such sales would not enter the head of most continental European politicians, because great architecture is considered a wise and enduring investment. If the Hotel des Invalides in Paris needed a new use, we can be pretty sure that the Elysee would have one up its Pierre Cardin sleeve.

The fact that the Government can think of no good use for Greenwich, for Admiralty Arch, for the Midland Grand Hotel in St Pancras, let alone a host of less distinguished buildings it feels overburdened by, is something of a mystery to observers on the other side of the Channel.

This blindness to the value of architecture (the way it is valued in a people's, and thus an electorate's, emotions) is not the sole preserve of politicians.

British business executives can be equally unaware of the importance of beautiful or otherwise characterful buildings. When Japanese investors have bought in London, they have been careful to snap up prestigious buildings of known architectural value, such as Bracken House, former home of the Financial Times, opposite St Paul's Cathedral, designed by Sir Albert Richardson and rebuilt by Sir Michael Hopkins. Or else, like Mitsubishi, they have invested in prestigious sites like Paternoster Square on the opposite side of St Paul's.

True, the Japanese, like other foreign investors (notably the Swedes) overspent on prestigious buildings in the late Eighties and suffered badly as a result after the City crash in 1989. This temporary set-back has not dimmed their genuine interest in high-quality design.

What is mysterious, however, is the fact that Mitsubishi has propped its vast weight behind the proposed, and banal, post-Modern classical redevelopment of Paternoster Square.

"Mitsubishi would never think of commissioning such a retrograde design in Tokyo," says Tadanori Nemawashi, one of the shrewdest investors in London's architecture. "However, they are too polite, and far too wise, speaking politically, to say so in public. There is no doubt, though, that they can see the difference in quality between, say, Alexander Fleming House [the former DHSS head office at the Elephant and Castle, south London] and the Royal Naval College, Greenwich."

A part of the Government's difficulty in distinguishing between property and architecture, and then between good and bad architecture, is that there are any number of voices trying to tell the Government what to think.

What, for example, would you do with Alexander Fleming House? Designed by the garrulous and sometimes brilliant Hungarian emigre, Erno Goldfinger, Alexander Fleming House was designed in a style known, unashamedly, as Brutalism. It was certainly brutal. Yet, when the issue of demolition was raised in the early Nineties, what seemed like a clear-cut case of "here's a building that's got to go" was instantly clouded by arguments, many arcane, in its favour.

The case of Alexander Fleming House brought many fogeys who had spent years railing against Modern architecture (whether beautiful or not) into the Brutalist camp. Last year the National Trust took the case for Erno Goldfinger to its logical extreme by buying the late architect's home (a terraced house designed by Goldfinger) in Hampstead, London.

Many warmed to Goldfinger once he was dead - and thus easy to deal with and classify. The real-life Goldfinger was an intellectual lion; he roared and terrified the very sort of people who now claim to admire him. And, of course, they were his enemies 20 years ago.

Born-again Brutalists and other converts to Modern architecture, appear, like government ministers, to have difficulty distinguishing great architecture from the merely aberrant, the good from the bad, beauty from the beast. So much so that bodies like the Twentieth Century Society openly support the retention and preservation of routinely drab office and other workaday buildings from then Fifties and Sixties. Bizarre as this might seem, it is really only a case of a typically end-of-platform British enthusiasm for the arcane. As railway enthusiasts have always sought variety and numbers above efficiency and beauty, so today's architecture buffs reveal an uncritical view of Modern architecture.

Until architecture, design and the culture of making things is a part of our general education, as opposed to specialisms that have to be learnt much later in life, the difference between good and bad architecture, between architecture and property will continue to elude the Portillos and Bottomleys of this world.