There's nothing so unattractive as vanity... particularly male vanity.

I'll probably always be 'Timothy Spall's son' and it's something I'm proud of. Maybe one day as well as that, they'll say of Timothy Spall that 'He's Rafe Spall's dad'.

I've done loads of things people have never seen, dramas on BBC4 and plays upstairs at the Royal Court and the Bush, and because I didn't go to drama school, they gave me an education.

In any kind of comic scene you're going to perhaps push the boundaries of plausibility but as long as there is some semblance of logic I think as an audience you'll buy it and as an actor, when it comes to playing things like that, it gives you something to delve into. When I don't buy into a comic scene is the type of scenario where you'd just go: "Well, that would never happen."

You do stuff that gets a reaction and you think 'that's a winner' and then it never sees the light of day. But the thing with improvisation is that 90% of what you come up with won't be used and for good reason. But you keep going for the occasional gem that you might come up with. You do a scene and a lot of the time. We wouldn't cut. So, you come up with something that might be funny and then you go, 'alright, what else'? So, you kind of throw stuff against the wall and see what happens. But you've got to be prepared to make a fool of yourself.

I watched what I ate for a bit and did a bit of exercise. I wanted to look alright because I knew I had to take my clothes off and I knew I was starring alongside some extremely attractive women! I think it was Humphrey Bogart who said that the only reason people found him attractive was because of the attractive women he played opposite. So, as audience member you go: "Well, if she would find him attractive, then surely I must too!" Playing opposite beautiful actress of the calibre of Rose Byrne and Anna Faris is amazing - it does a lot of the work for you.

I love doing comedy, I really do. It was perhaps my first love. And I think, as an actor, you're young and you do school plays and the reason you go 'I might do more of this' is because you make people laugh in a school play. You don't go and do Hamlet when you're nine and go: "I feel people were really moved out there!" You do a silly voice and everyone laughs and you go: "Ooh, that feels quite nice. I might make a life out of this!"