Making 'Birdsong,' on the one hand you have how prestigious it is and the reputation of the book, which is something that's an extraordinary piece of work. Sebastian Faulkes is a genius. So you feel that responsibility when you're portraying that character that he's imagined and millions of readers have pictured.

I'm quite ignorant about fashion and I'm colourblind, so it's all a tad tricky. My only knowledge of that world comes through Christopher Bailey, whom I first met in 2008 when I did a campaign for Burberry that featured musicians, artists, actors and sportsmen.

It's the weird thing Eton does - you're at school next to lords and earls and, in my case, Prince William, so you end up being used to dealing with those sorts of people.

And you can't complain about kissing Emma Watson. Isn't that what everyone in the world wants to do? I've known Emma for a few years. She's this amazing capacity of young and vibrant and brilliant, but also a bright, intelligent old soul.

Most actors hate watching their own films because all you can see is the glaring mistakes, your own tricks and ticks.

As a runner on a film, you are the lowest of the low, and yet you have incredible access to everyone. I can totally imagine that for actors in the middle of a Hollywood bubble, all they really want is a sense of normality, and that gopher can be a tap for that.

People ask, "Do you enjoy acting?" But you only have those specific few hours to do a scene, and then you drive home and wait for six months to find out how it went. You can't go back and put in a new idea. Filming is about continuing to be alert and to think, and I find it quite exhausting. Certainly I would say that fear is a part of that.