But now sustainability is such a political category that it's getting more and more difficult to think about it in a serious way. Sustainability has become an ornament.

In a script, you have to link various episodes together, you have to generate suspense and you have to assemble things - through editing, for example. It's exactly the same in architecture. Architects also put together spatial episodes to make sequences.

There is no plateau of resting or stabilising. Once you are interested in how things evolve, you have a kind of never-ending perspective, because it means you are interested in articulating the evolution, and therefore the potential change, the potential redefinition.

It was a book [George Packer written on our presence in Nigeria] that was killed by the response of other people. Which sounds quite cowardly, perhaps, but it was the first manifestation of what is currently a really big issue: how political correctness defines the limits of what you can do. In that sense, it was super-exciting and maybe the most magical project we did, but at the same time fraught with mixed feelings.

The people from the suburbs are bringing along their suburban values: cleanliness, orderliness, safety - dullness, in other words. As a result, urban areas are being hollowed out. Just look at Times Square in New York. No more sex shops, no drugs, no homeless people. The area is clinically clean and incredibly dull.

Sustainability has become an ornament.

Nigeria was a blank on the map - there weren't even any maps. The US State Department, everyone said don't go there. It was courageous of Harvard University: the notion was that we would match Harvard students with Nigerian students, so that every student would have a guide, creating a guarantee of intimacy with the city.