The Doctor does battle with mysterious Missy and old foes the Cybermen in a two-part thriller (Saturday, BBC1). Chris Addison tells TV & Satellite Week all about co-starring with his old The Thick of It co-star Peter Capaldi…

Tell us more about your character, Seb, who seems to be a kind of receptionist in Missy’s Nethersphere?
“I’d describe Seb in four words: Polite. Charming. Hiding. Something.”

How did it feel to get asked to appear on Doctor Who?
“Stupidly exciting! It’s the phone call every actor wants, isn’t it? It came entirely out of the blue. I had no idea about it. My agent, who isn’t usually given to excitement, rang me one day and said, ‘You’re going to want to sit down for this…’

Were you always a fan?
“Absolutely. I joined halfway through the Tom Baker years – I think The Stones of Blood in 1978 was the first time I was ever truly scared as a child – and Peter Davison was my first, proper Doctor. One of my great disappointments in life was not being able to snag a toy Tardis at my school Christmas fair in 1981, priced 50p. My wife bought me one a few Christmases ago to make up for it.”

Michelle Gomez plays your boss, Missy. How scary is Michelle in real life?
“As a person she couldn’t be more fantastic. As Missy, she’s absolutely terrifying. She’s a great villain for Peter’s Doctor, actually, because you never quite know where you are with him, and Missy is like that too. It’s madness meets madness, and you’re caught in the middle.”

Why are the Cybermen such enduring villains?
“I think it’s the same thing as the Daleks: it’s their inhumanity, the fact that you can’t appeal to them in any way. They’re so numerous, too. In the old days you never really saw villains like the Sontarans in massive numbers, because how could the BBC possibly afford to do that much make-up? A Cyberman is basically a costume, so there can be thousands of them, and that’s terrifying.”

This episode contains one particularly huge reveal. Did you see it coming when you read the script?
“I was furious with myself for not seeing the big twist. Though to be honest I wasn’t paying much attention to the story at the time. I was mainly thinking, ‘Am I going to get a scene with Peter?’

What was it like reuniting with him?
“As I was being fitted for my costume, I heard his voice, asking where I was, and then he came bounding into the trailer, dressed as the Doctor. He showed me round the TARDIS and I sat in one of those canvas film-set chairs and watched him do a scene as the Doctor with Jenna Coleman. It was amazing.”

Will The Thick Of It ever come back?
“I don’t think so. Maybe one day, years into the future, there will be some subject that so annoys Armando Iannucci that he wants to return to it. But I think we ran those characters as far as we could. I owe Peter an awful lot. He took me under his wing when I started on The Thick of It, because I hadn’t acted before.”

Who is the real Peter more like: Malcolm Tucker or the Doctor?
“One of the things about Peter is that he’s relentlessly funny. He’s also a thoughtful, interesting man. So I think he has the charm part of Malcolm – because Malcolm could actually be quite charming – and the impish part of the Doctor.”

How would your The Thick of It character Ollie cope in the Nethersphere?
“Oh, he’d freak out. I mean, he would think he could cope. But he would freak out. Ollie’s not made for the big game.”

Weren’t you one of the bookies’ tips to be the next Doctor at one point?
“That came from a prank by my friend Geoff Lloyd, who has a show on Absolute Radio. He got Paloma Faith to tweet, ‘A friend of mine who works on Doctor Who says Chris Addison is replacing Matt Smith – WOW’ and then delete it almost immediately. In the bookies’ information vacuum, that was enough to make me one of the favourites.”

Would it appeal, if they asked you one day?
“I doubt it would ever happen, but of course it would appeal. It’s a show that I’ve loved for 35 years. How could you say no to that?”

What would a Chris Addison Doctor look like?
“Ha! That’s a smart question. I wish I was smart and thoughtful enough to answer it, but I can’t. I’ll have to give it some thought…”

If you had a TARDIS, where would you take it?
“I’d like to go and see what’s at the centre of the Milky Way. Let’s go and have a look at that bright bit. What’s that all about? That’s where I would go.”