Other new towns were built on piazzas designed to house compulsory bits of Henry Moore: but the Walking City rests on four pairs of neat, telescopic pins. Herron being a purist in such matters, these weren't merely decorative. The City's legs were intended to propel the entire city slowly around the globe at the whim of an invisible driver. It is as if somebody had spiked Le Corbusier's cocoa and the Unite d'Habitation had wandered off on its pilotis.
What was the Walking City all about? "Technology," is certainly one answer. Examine Herron's drawings for the project and you will find the same Sixties ambivalence towards the technocratic future - part-romantic glorification, part-apocalyptic terror - that underlies almost every other popular art work of the period: Dr Strangelove, Stingray and Peter Blake's design for the cover of Sergeant Pepper, to name but three. Herron may well have meant his peripatetic town-bugs - as his rubric suggests - "to house a large population of world traveller-workers". But they looked as though they would have stopped to eat the rest of humanity first.
Mostly, though, the Walking City was about Archigram: a group of six young architects - Herron, Peter Cook, David Greene, Dennis Crompton, Michael Webb and Warren Chalk - who took their name from the broadsheet they launched in 1961, and whose work forms the subject of a sizeable retrospective which opens at Manchester's Cornerhouse gallery next month.
The word "Archigram" - from "architectural telegram" - was intended not just to suggest the sporadic nature of the magazine's publication but to flaunt it. By so doing , the sextet hoped to provoke more sedate periodicals, particularly the Architect's Journal, into writing about them. It worked. In 1961, the AJ - gratifyingly wrathful - devoted a whole double-page diatribe to Archigram, denouncing the group, the magazine and all its works as "neither with it nor sick, but sad". The Fab Six had arrived.
It is easy to see why the whole thing irked so. Archigram were not the first group of professional tyros to thumb its nose at its academic elders - the Impressionist Salon des Refuses had beaten them to it by a good century - but it was the first to suggest a particularly shocking form of subversion: the idea that architecture not merely could but should be viewed as disposable. The credo underlying all of Archigram's work - whether a piece of fantasy like the Plug-In City's clip-on bedrooms (1964) or the group's only almost-built structure, the Monte Carlo Entertainment Centre (1970) - was that buildings should change as the uses for them changed. In the phrase of the critic Pascal Schoening: "To the three classical dimensions of architecture, [Archigram's members] chose to add the dimension of time."
It was not a popular choice. Arguments may have raged back and forth for centuries over the proper use of the classical orders; blood may have been spilt on the honesty of load-bearing walls; but even Corb had not been cheeky enough to question the notion that buildings should be designed to last. When Peter Cook blithely opined that "the pre-packaged frozen lunch [was] more important than Palladio," he did for architecture what Warhol was already doing for fine art: he reduced it to that most Sixties of things, a consumer durable. He also reduced the architectural establishment to highly useful paroxysms of rage.
"One's first exposure was really in that AJ piece," mused Cook, speaking from the HbK art school in Frankfurt, where he now teaches. Now 61 and still unrepentantly media-aware, Cook goes on: "The chap who wrote it suggested I read Descartes' Discourse on Method for some reason. I did go out and buy it, actually, although I still can't see why he recommended it. What mattered, though, was that he took two whole pages to make the recommendation."
Pausing sweetly, Cook adds, "Oddly enough, he himself disappeared completely from view shortly afterwards."
Not so Peter Cook. Although Archigram's chosen aesthetic was self-consciously throwaway - Archigram the magazine was held together with staples, its graphics an open homage to the disposable trashiness of Roy Lichtenstein - the evangelists of impermanence were themselves to prove ironically durable.
This is all the more droll because the Establishment view of The Six has long been that they were a group of lippy onanists who couldn't have built a building if they had tried. (It has to be said that - with the notable exception of Ron Herron, perhaps most famous for the Imagination building in London - Archigram's members have built remarkably little.) On the rare occasions when the group did actually try to build something, runs the story, its members couldn't handle the responsibility. (In fact, the Monte Carlo Entertainment Centre project, which those same members won in an open international competition in 1969, failed to be built because Prince Rainier changed his mind. Archigram, always more a loose alliance than a working architectural practice, closed its office soon afterwards.)
But Peter Cook is especially annoyed by this version of events. "Look at drawings for even the so-called utopian projects like the Plug-In City and you will find that there are always workable elevator shafts, always in the right place and always drawn to scale," he says. "If we were going to suggest that something in a drawing might be built in plastic, then we all trooped around plastics factories to find a plausible material."
All this is as nothing compared to the view that holds Archigram responsible for poisoning the minds of the nation's architectural youth, though. Go to the most prestigious architecture schools in Britain, runs this theory - the Bartlett, the Architectural Association, Westminster University - and you will find members of the cell (Cook, Crompton, Greene, in that order) openly encouraging students to submit videos or neon installations for their diploma shows instead of doing technical drawings or making maquettes of suspended ceilings. It's the kind of thing that leads directly to avant-gardists like Zaha Hadid - and we all know what happened to her Cardiff Opera House project.
In fact, if Cook and his gang have managed to recruit a generation of Archigrammic fellow-travellers, they (like Hadid) have little enough to show for it in concrete terms. Cook himself suggests that Archigram's few real followers have largely come from Japan. As far as European Archigrammery goes, the building most widely viewed as influenced by the group's ideas - the Pompidou Centre in Paris - was built in France, by a pair of architects, Renzo Piano and Richard Rogers, who between them were three-quarters Italian. In any case, hmphs David Greene, merely having moveable interior walls does not make a building echt Archigram. "If the Pompidou had really been one of ours," he sniffs, "it probably wouldn't still be standing where it is today."
In fact, David Greene's melancholic view is that "Archigram probably had almost no real effect on British architecture at all". For him, the most potent symbol of this morose truth is in fact Britain's tallest building. "Canary Wharf is a built denial of everything that Archigram stood for," he says, sadly. "While the way offices are used has changed enormously - most business is probably now conducted in the street or in restaurants by guys on mobile phones, in fact - you still get people putting up the kind of great big lump that hasn't essentially changed since office building began. What's that lump all about? It's about money: it's a financial object, an investment rather than a building."
For his part, Peter Cook does at least sense a darker victory. The Archigram exhibition, already on the road for nearly three years, has drawn crowds in Vienna, Paris and New York. Now that it has finally made it to Britain, the show has been shunted off to Manchester. Attempts to find a home for it in London, according to both Cook and Greene, met with no support at all .
"I have a private theory about why that should be," says Cook. "I suspect that perhaps some of the more famous British architects - offices to which we still feed an enormous number of students - find it difficult to admit that they owe their start to Archigram. It would underscore the fact that they're not so original after all. I suppose we ought to find it all rather complimentary."
Cornerhouse, 70 Oxford St, Manchester (0161 228 2463), 9 Jan to 15 Feb; free.
The gallery is holding a symposium - "ARCHItectural teleGRAM: sending out a vision of the future?" - on 9 Feb; tickets pounds 10 (pounds 6 concs).