So what you get, if you order an M-house, is a core structure with a choice of finishes and layout. It is offered in cedar planks or shingles, in a weird flat patterned aluminium that looks like solid gingham, in painted timber like your classic beach hut, or the corrugated aluminium that the show house comes in. There is even a floating version proposed, for the houseboat market. Since it is engineered to need no internal support, you can place your partition walls where you want, and put the windows and sliding doors in different positions (on the prototype there is a long low window placed just above the bath, for staring out in contemplative fashion). The idea is that - once you've specified it the way you want - there is a 6-week delivery period at a fixed cost. It arrives in two halves on lorries, is rolled or craned into place on prepared pad foundations in just one day.

Just because something meets the definition of a caravan, does not mean you can drop M-houses around everywhere without bothering to contact your local planning authority. For a start, the land has to be zoned for residential use. Even if it is, then not only the planners but also your neighbours might have something to say about an object this size landing in a small back garden, for instance. However, in theory at least there should be no quibbling about the design of the thing itself - only its siting. Which, since these things are removable, is maybe less of an issue than it might be. Official reaction to an M-house in a sensitive bit of overlooked urban backland, for instance, has yet to be tested.

I like the M-house. It's real architecture, well made, nicely detailed, inside and out. It represents ingenious thinking. And it certainly isn't aimed at the trailer-trash market. Although Pyne has produced some beguiling montages of the house perched on top of old buildings in London, it will probably appeal most to people seeking a different kind of rural retreat. But such people aren't going to want to be surrounded by tin boxes in rows. It's the usual problem: you've got to find yourself a site. Given the ubiquity of caravan parks around the country, maybe that's not so difficult as you might imagine. Step one: find yourself a friendly farmer.