‘Newborn twins? They’ re tough er than a maximum-security prison!’

How was going into prison?

I was nervous. I had to go in as a prisoner, so I actually had to strip naked. You felt the slight humiliation and the removal of your life – you hand over your credit card, your watch, your mobile phone…

Who was the most shocking prisoner you met?

I met a former school teacher who had downloaded sexual images of children. He didn’t think there was anything wrong with that, or that he should be in prison, and he said he would never stop being attracted to children. I couldn’t stay impartial. I didn’t shake his hand.

Were there lighter moments?

No, it’s me. I don’t do lighter moments! Although I was helping make sandwiches with a guy who was in for attempted murder. We were chopping up the food with these big knives and I discovered he’d stabbed somebody in the face with a carving knife!

Your wife has just given birth to twin girls. Which is hardest, newborn twins or going into a maximum-security jail?

Newborn twins, 100 per cent! And to add to it, Leo [two] got chickenpox the day we went into hospital. So he’s ill, he’s missing his mum, and then she comes back with these two babies who are taking all her attention. The twins are on three-hourly feeds, and Leo’s not sleeping at the moment.

It sounds exhausting!

It’s great! I’m relatively late to fatherhood, and I’m loving it. I don’t think I’d have been

prepared for it before – I was too immature.

Do you see yourself as a journalist or an actor?

I’m primarily a reporter and a documentary maker; I used to be an actor. I changed careers at 37. One minute, I was pretending to be shot at in Ultimate Force, and the next minute I was really being shot at in Afghanistan. You should be allowed to change careers – you shouldn’t allow people to pigeonhole you.

No more acting, then?

It’d depend on the offer I guess. As for EastEnders – never say never. It’s a great show. Ross Kemp Behind Bars – Inside Barlinnie is on Thursday 2 Nov, ITV, 9pm