You don't restore 'The Last Supper' by filling in the missing bits - you preserve. You accept the material that has somehow survived.

I spent more than ten years working on the Neues Museum. It was a wonderful experience, an example of real collaboration between architects, conservationists, curators, client, politicians, the media, and the public. Discussions, even when difficult, were always about ideas. Ideas matter to Germans. They're a reflective people. That's attractive.

Architecture has curled up in a ball and it's about itself. It has found itself either as a freakshow, where you're not sure if it's good or bad but at least it's interesting, or at the behest of forces of commerce.

I'm suspicious of the idea of architects acting like business executives, brand managers, or purveyors of luxury goods.

We see buildings in Britain mostly as freestanding objects. They are not meant to have a dialogue with anything around them, or with history, or with ideas of any kind beyond the self-referential. What we call 'regeneration' is largely an excuse for building for maximum profit with a bit of sculptural design thrown in to catch the eye of the media.

It is difficult to separate oneself from one's design moralities.

It used to be presumed that if you weren't at your desk working, you weren't working. But we said, why can't we make a workplace where casual meetings are as important as working at your desk? Sometimes that's where your better creative work happens.

There is a danger when every building has to look spectacular to look like it is changing the world. I don't care how a building looks if it means something, not to architects, but to the people who use it.

I think that the point of being an architect is to help raise the experience of everyday living, even a little. Putting a window where people would really like one. Making sure a shaving mirror in a hotel bathroom is at the right angle. Making bureaucratic buildings that are somehow cheerful.

I do very little industrial design. I'm asked a lot, but I certainly don't see myself as an industrial designer.

I don't think architecture is radical. How can something that takes years and costs millions be radical?

I like to be surrounded by books. My wife Evelyn has a PhD in comparative literature so we have a lot of her Spanish and German literature books which are wasted on me, plus a lot of novels and books on art and architecture shared by us both. Evelyn used to edit an art magazine called FMR, so we have a common interest in design.

The difference between good and bad architecture is the time you spend on it.

A building is no good if someone's got to explain to you why it's good. You can't say you don't know enough about architecture - that's ridiculous. It's got to work on many levels.

I suppose I'm trying to build an architecture that's as timeless as possible, although we're all creatures of our age.

If you look at a building by Mies van der Rohe, it might look very simple, but up close, the sheer quality of construction, materials and thought are inspirational.

Most architects work in ­studios largely divorced from academia, as if ideas, criticism and ­historical ­research were irrelevant.