We talk to The Office star on his transformation from office geek to military man in BBC1’s Accused

What was it like to play a career soldier?

“It is a serious thing to put on an authentic army uniform. I felt I didn’t really have the right to wear it. Here am I pretending to be a tough soldier when I haven’t been through the training and I couldn’t comprehend what these guys go through. But that’s my job, to pretend.”

Did you have to think long and hard about playing the role?

“It wasn’t like anything I had done before, and my instinct was to say this is not for me. But I quickly decided that was the wrong attitude. I need to do challenging roles, to stretch myself. So I went away for a couple of days, thought about it, and decided I would be a fool to turn it down.”

And it is very different?

“Yes. Some casting directors are not very imaginative. I get a lot of scripts that are for the strange, geeky character, but I’ve been longing for a meaty role like this to play, particularly in a television drama. It is a dream come true to do this. I don’t necessarily think that will stop the weird geeky parts coming my way, but we’ll see.”

What was it like having a disused quarry in Bolton doubling for Afghanistan?

“We were incredibly lucky with the weather. It was blazing hot sunshine. If it had been drizzly and overcast it would have been very hard to imagine that it was Afghanistan! But a lot of the extras were ex-military, and they said we’d got it right, that it was like going back to the Middle East. The first scene in the quarry was a big gunfight between the British army and the Taliban. It was hairy – obviously not as hairy as the real thing, but you are still firing automatic rifles with blanks and they are still as loud.”

Would you wants your son to join the military?

“I would like my son to do whatever he wants, but I’ve got to admit, that if he wants to join the military, my heart would sink. I just wouldn’t want him to be in the situation where his life is endangered. Not because I disagree with the military or anything, but that would be difficult and I would probably try to persuade him against it. I’d probably try to persuade him against being an actor as well, but happily so far he has shown very little interest in either of those career paths…”

*Accused screens on BBC1 on Monday night