I do think a good story in a novel is fair game and there's nothing wrong with adapting that. It sometimes gets a bit facile where they think: "Let's get the next best-seller and see if we can turn it into a film."

Firth - all dodgy 'tache and frantic eyebrows - has got the sexual allure of a man who runs a swingers' club in Surbiton.

I'll be your friend so long as you're not crap

I do also think it eludes genre a bit - not in any groundbreaking way but you can't quite call it a comedy and you can't quite call it a romantic anything. It's not quite a drama either really. But it has elements of all those things.

I do notice that when I've been away and I come back to London. People look at you. People are ready to pick arguments.

So, if you haven't picked up some tips during an apprenticeship like that, you shouldn't be directing. It doesn't mean you can do it, but it loads you up with information.

I think that London is very much like that. I find there's humour in the air and people are interesting. And I think that it's a place which is constantly surprising. The worst thing about it? I think it can be smug and aggressive.