The former EastEnders actor, who plays King Cenred in BBC1’s Merlin, reveals what’s in store in the nail-biting two-part finale to the series…

Evil King Cenred’s back again this week for the first in a thrilling two-part finale. What can you tell us about this episode?

“It’s a further attempt for Morgause to push Morgana to become Queen of Camelot and, once again, they enlist Cenred’s help for manpower. There’s a cup of life, a powerful magical artefact which carries the gift of immortality to anyone who drinks from it after shedding their blood into it.

“Morgause gets hold of it – conveniently – and, with Cenred’s men, creates an immortal army to try to take over Camelot again and make Morgana the Queen. This time, however, you get the sense that Cenred might be in it more for himself than you may have thought before. There’s no ‘I’ in team is applicable in this one. Never trust a baddy! There are some great battles to look out for. They are brilliant episodes and a grandstand finish to the series.”

What have you made of this series?

“It’s been really good! I’d not watched a lot before, but I love it now whether I’m in it or not. My daughter loves it, too. I think it’s a really big achievement for the BBC in terms of production values as well. It’s one of those great shows you can watch with the whole family.”

What do your daughters make of you being in Merlin? [Tom has two-year-old Florence with his wife, actress Tamsin Outhwaite, and four-year-old Nora from a previous relationship]

“Both my daughters are both so unimpressed when they see me on television. I want them to say, ‘Oh, Dad!’ But I say, ‘Who’s that?’ and they say ‘Dad’ with no real interest, even if I’m wearing a long wig and riding on a horse! I think I’ll have to read a CBeebies bedtime story instead.”

Did you like the king’s costume?

“Oh my gosh! I loved it! It was the best costume I’ve ever worn for anything! It was tailor-made for me, the most ridiculous leather suit which I could barely move in and an OTT wig. I looked a bit like Russell Brand really, so I’ve been told. An evil Russell Brand. I had a lot of fun playing a bad guy – the way it was written in some scenes he was almost a panto-esque baddie, or a Bond-like villain. It was possibly the most fun I’ve ever had on a TV set. I got to do everything I ever wanted to do when you’re a kid.”

You’re such a lovely guy – it must have been hard to play mean, though?!

“The funny thing is, I had to do a scene with Angel Coulby, who plays Gwen, where I had to pretend to hold a dagger to her throat and then cut some bonds from her wrist. I was being really mean and nasty in the scene when the tip of the pretend knife touched her skin, but I was immediately back to me and ‘Oh my God, are you all right?’ But I’ve loved playing nasty! I loved the job as a whole.”

What were your favourite stunts during the past series?

“Well, I got to ride a horse which I was a bit nervous about as I hadn’t done it for ages. But I got a lovely black horse called Mr P and we got on famously. He made me look much better than I am. There’s lots of horse riding in heavily wooded areas so a lot of hazards, especially as I’m already 6’3, so, on a horse, I’m pretty much branch height.”

What action shows did you watch growing up?

“I used to watch Robin Hood – Robin of Sherwood on ITV which starred Jason Connery. Michael Praed, too. My mum and dad were always into costume dramas so I would always watch something I didn’t understand, but looked very pretty.”

What TV shows do you like now?

“The TV in my house is dictated by my daughter. I don’t watch an awful lot, but I did watch The Silence recently (a BBC drama about a deaf girl witnessing a murder). I’ve been really into the new Sherlock Holmes, too. Benedict Cumberbatch is fantastic.”

What shows have you introduced to your daughter?

“I’ve started introducing her to films. She’s already obsessed with Mary Poppins. She watches it on average once a day – with a lot of fast-forwarding – in the morning with her milk or in the evening with her milk. Or the 1958 version of Tom Thumb.”

What’s next for you?

“I’m heading out to LA again in January. I was there a few years ago and did a pilot with Fox, which was great, so I’m going to go again and see what happens.”

*Merlin screens on Saturday at 7.45pm on BBC1