How does an architect follow the Guggenheim?

Frank Gehry flew into London to give a lecture at the Royal Geographic Society which could have been subtitled "What now? after the Gu". The Guggenheim not only put Bilbao, a Basque chemical factory town on the map as an international resort. The tensile titanium gallery, an icon of the late twentieth century, made Frank Gehry the world's most famous architect.

The ebullient London crowd loved the slides Gehry showed of the twin towers in Prague that he calls Fred and Ginger, his wavy duo of dancing buildings; the aluminium onion suspended inside an atrium for conventions at the Brandenburg Gate in Berlin; and the billowing sails in curved wood for the Disney concert hall he designed in San Francisco.

Gehry also showed slides of models of some of his works in progress, a rock 'n' roll museum in Seattle; his glossy new canteen for the Conde Nast offices in Manhattan hasn't been completed yet, but Vogue has already booked it for a fashion shoot.

The slide show, coupled with Gehry's sweet smile, self-effacing manner and his confiding that the Basques in Bilbao wanted a "Sydney Opera House - something that fantastic", so he thought "yeah, well I'll try" wowed the crowd.

They were shown plans for Gehry's first building in Britain, the Maggie Keswick cancer centre in Dundee. The project is supported by celebrities such as the actor Jeremy Irons and news presenter Jon Snow, who were rattling collecting boxes outside to raise money for the Maggie Centre.

The late Maggie Keswick Jencks was a landscape designer and wife of architect and critic Charles Jencks. She was a friend and colleague of Gehry's, having met him in California in the Seventies where Charles Jencks was lecturing. Gehry has waived his fees for designing a cancer care centre in her honour.

As buildings go, it's modest, only 250 square metres and with a budget of half a million pounds. The centre - if funds can be raised to get it off the ground - will be built alongside the NHS hospital Ninewells,where some of the world-class oncologists are working on cures for cancer. The NHS have let the Maggie Keswick Trust rent the land for one penny a year for fifty years to open their second Maggie centre. The first, bequeathed by Maggie in 1996 before her death from cancer, is attached to Edinburgh Western General.

The centres are holistic places for people with cancer and their families to seek advice, therapies, diet information and support.

Like all the things that mean a lot "too much" the design is causing Frank Gehry heartbreak. "There was a modesty about her that I did know and recognise," he says. Modesty is a word that comes up a lot. Determined to make a tribute to his friend that would put Dundee on the map, he and a team of 150 people worked on models in his studio in California for three months. He created up to 50 or 60 of the working models - in old Blue Peter-style with loo rolls and silver paper and boot jacks and perspex - after defining volumetric spaces in sugar cubes.

But no sooner had they defined the final one in September to send out for costing than Frank bottled out of it. "For three or four months I'd made endless models with a nagging feeling," he explains. "It was a little bit too immodest. Beautiful, but losing its modesty."

The roof had a double curved dome, with a great ocean wave of a roll surging over to form the walls in a membrane of steel or zinc - not titanium, too expensive - and a castle keep at its core. He describes "Scheme Zero", as it is now known, as "My chance to design Ronchamps", a reference to Le Corbusier's chapel at La Tourette in France. His only epitaph to the shelved models is: "Pretty nice, friends saw them and everybody liked what they saw."

His new solution has a corrugated roof that fans out gently, and irregular rises and falls over the ground floor provide an affordable and uplifting environment for cancer patients and their families. It is being costed by quantity surveyors now, even as contractors are awestruck at the notion of building a Gehry. "My fantasy is that it is built by locals and carpenters with a wooden frame and exposed exterior, plaster walls and a corrugated roof," he says.

He also wants the hospital to move the helicopter pad from in front of the building: it destroys the serenity of the place when helicopters fly in three or four times a week. Instead, in the ground he wants to put a pond and an island for the helicopter to land, connected by a bridge, all in memory of the bridge he built with Maggie Keswick Jencks in Cleveland. There she also designed a one-foot red-coloured runnel finished in glass that zig-zagged through trees and changed to blue as it zig-zagged out the other side of the forest. "It was all about life and death, and shows me that Maggie was thinking about it."

Contact the Maggie Jencks Keswick Cancer Care Centre if you are interested in supporting it, 0131-537 3131