It was an army hut with a view. Now it is becoming an `elegant cave', after a maverick architect and a Labour MP conspired to build a thing of modern beauty on the Welsh cliffs.
This is the story of an architect, an MP and a Nissen hut. The architect is London maverick Jan Kaplicky. The MP is Labour's Bob Marshall- Andrews. And the Nissen hut? Well that's where the story starts. Many years ago Bob Marshall-Andrews and his wife Gillian came across the thing perched on a clifftop in Pembrokeshire. It had been there since the 1930s for no useful reason. "It was a blot on the landscape. We kept looking at it and seeing how ugly it was but couldn't help but think what a wonderful place it was to be ugly," he says. "Then somebody told us it was for sale. And so we bought it. We didn't pay much. It's the sort of money you pay for an army hut with a view."

They then waited for inspiration. Years passed and one day they happened to see a programme on Jan Kaplicky and his firm Future Systems and its innovative Glass House in Islington. "They seemed to be everything we wanted. They were modern, dynamic and ecologically friendly. So we called and said: `We've got this Nissen hut...'"

Now these are not words that inspire most architects but Jan Kaplicky is hardly that. So they all trooped off to Wales to see the hut but the weather had other ideas. The rain was horizontal, the sea angry and a dead whale had been thrown up onto the beach. It sounds like the site meeting from hell. "It can be Siberian there. Dreadful! I mean I love it but it's not Jan. He is very elegant, very composed. I think it came as a frightful shock," says Bob Marshall-Andrews.

The result of that weekend may come as a bit of a shock to others too. The Nissen hut is gone forever. In its place, one will only see only grass. This is the roof of a new home that Bob describes as an extremely elegant cave. And, as befits the offspring of the Nissen, the view is to die for. The next whale that washes up will see what looks like a gigantic glass eye carved into the cliffside. It has to be one of the most beautiful picture windows in the world.

Jan Kaplicky claims it was a great challenge to create something that did not just blend in with the environment but was the environment. "Any architecture would look ridiculous in that place," he says. "You have to think what the hell am I going to do there. Everything is unspoilt. How do you compete with that?" In the end, he didn't even try. "There is only the grass and the glass. Nothing else, no architecture. Everything else is hidden. There are no vertical walls. There is only a glass wall that overlooks the sea."

On the face of it the MP and the architect make an odd couple. Jan Kaplicky is Czech - he fled here in 1968 - and has his country's sadness about him. He is tall and speaks softly, slowly and sometimes only with coaxing. Not so Bob Marshall-Andrews. The MP for Medway is brisk, boisterous and explosive. I make one mention of the Millennium Dome and he is spitting within seconds. "The wretched thing is just a big hut made of Teflon! Everything inside is made of ticky-tacky or plastic. It is a ghastly theme park. It has no art, no adventure, no redeemable features. It is a monument to the ego of a limited number of people or, if you want to be pretentious about it, the ego of mankind." Wow. I ask Jan what he thinks but he wouldn't like to say.

Jan Kaplicky founded Future Systems in 1979, but its work was usually considered too daring to build until recently. (The notable exception being the Glass House in 1994 which became famous in less than 15 minutes and has stayed so). He is a man of few compromises. His work is ecologically correct and he likes to "break the box from the outside" . He can be very practical and perhaps naive too. Thus he designed an electric bus because he hates the smelly, noisy one he has to ride on and a barge that he calls a "boatel" to offer emergency beds for the Embankment's homeless. He is bitter about the lack of interest in such things. "The boatel design was never published, it was never shown and that was that. That's the world. People don't want to know about the homeless. It spoils the dinner parties."

He talks of beauty as if we all know what it is. In fact, he does seem to know and insists that everything, from trolleys to champagne buckets to buildings, should have it. His office certainly looked pretty good to me. Even the coffee cups had that certain something. The wall was a very particular and shocking shade of fluorescent yellow and the one-off carpet is fabulous purple. Architecture, he says, no longer cares about such things. "The uglier the thing the better these days. Ugliness is the norm." He points out the window of his office near Edgware Road at the rather ordinary building. "I would love to see some of the faces of the people who create this ugliness. I'm sure they have never had a date or anything. Can you imagine what the man who built that's private life must be like?"

Doesn't he mind that so much of Future Systems work has stayed on paper? He shrugs. This is a different issue from the boatel. That is about society's indifference, this is about professional integrity. "You have to divide people into categories. Some architects build very little but change things. An American architect, Charles Eames, built two houses and he pushed things dramatically. I think it is a total fallacy to judge people by how many tons of concrete they use. There are big firms on this planet which are building tons and tons, but without any intellectual or architectural value. I think we are getting so commercialised that this aspect of architecture is almost forgotten. Somebody has to push the limits. Maybe we are here for stretching the limits. Of course it is not a very commercially desirable role because you are not getting rich. But I don't mind."

But something strange and unsettling has started to happen to Future Systems. It has always been tiny (it is six people and Jan's partner Amanda Levete is a co-director) but now it is being seen as perfectly formed as well. It is, in fact, becoming fashionable. It has built the pontoon bridge at Canary Wharf, the tiny Wild at Heart flower shop in Notting Hill and, of course, there is the house in Wales. Its new space-age all- aluminium media centre for Lord's Cricket Ground opens this September and it has designed a revolutionary building called The Ark for the Earth Centre at Doncaster.

So the mavericks are now working for Lord's Cricket Ground and Members of Parliament. Whatever next? Jan won't like giving up his outsider status - "some people stay a bit outside of fashion and maybe they have a certain advantage" - but this week he will have to. Because what is next is an exhibition at the ever-trendy Institute of Contemporary Arts. It opens on 1 April and the idea is to anticipate the interest in Future Systems and the Lord's media centre. The exhibit will have 53 models (on two curvy fluorescent yellow tables) and 140 drawings. The carpet is a very particular shade of pink. Why pink? Jan answers, for once quickly: "My answer has to be, why not pink?"

There is no pink (or purple) in the elegant, three-bedroom cave and, when it is finished in two months, it will be mostly white. But by now I am beginning to realise that the MP and the architect are not the odd couple at all. They see many things in the same way - the boatel and environmentally correct living to name but two. And isn't it strange that two men with such left-of-centre views have created such an home? It seems a wealthy thing to have done. Both hate this idea. "I'm not going to tell you how much it cost, but it is considerably less than a comparatively small house in a reasonable part of London," says Bob. Jan insists it is a modest residence. But it is not. A Nissen hut is modest, a glass eye something more. So now we know the moral of this story: that even an ugly Nissen hut can turn into something beautiful. Eventually.

Future Systems exhibit opens at the ICA,The Mall, on 1 April.