Matt Smith, Karen Gillan and Arthur Darvill prepare to face their greatest fear…

Matt Some people say a Dalek is just a pepper pot moving around, but from my character’s perspective, it’s an alien psychopath trapped in a tank. Do you know what I mean? That’s what’s so scary - they’re nuts and they’re in a tank of armour with guns and lasers and suckers.

Arthur This script does make them really scary, but I got a lot of amusement from the times on set when they didn’t have “the voice”. The operators have to hang around the studio for hours, so they do chat to each other. It’s as if when the Doctor’s not there, they can talk normally, but then when he returns, it’s like, “Oh God, he’s here now, we’d better do the voice.”

Karen I did try to have a go inside one Dalek, but I almost broke it, so I had to leave it alone. It was really special and old.

Matt The one from 1963 is so cool. I did use the voice changer, which is brilliant. One of the Daleks that we used - a black one - actually belongs to Russell T Davies [Doctor Who’s showrunner, 2005 2010].

The Ponds days are numbered  - feeling nervous?

Arthur The script read-through for episode five was emotional. I had my hand on Kazza’s back, trying to help her get through it. But I didn’t want the actors who’d come in for just one episode to think we were really self-indulgent because we were all crying. It must have been really weird for them.

Karen To be honest, though, you’d have to be dead inside not to cry at it. Steven Moffat knows exactly what he’s doing when he’s tugging on the old heartstrings. I will miss filming the show, even the early starts and eating poached egg and grilled tomato at 6.30 in the morning. It helps to be in a good sleep pattern and routine but, you know, running away from aliens is something that’s easy to get up for.

Arthur For the die-hard fans, there’s a lot of exciting stuff in these episodes where I’m just thinking, “They’re going to go nuts about this.”

Matt For me, it’s sad to see them go as I’ve developed such wonderful relationships with them both. But one has to embrace change on Doctor Who or it leaves you behind. Forward is the only way to look, really.

Karen After filming, though, I did take some binoculars from the Tardis set, so they’re now mine. Nobody would have known if I hadn’t jumped around straight afterwards and gone, “I’ve got the binoculars.” My cover was blown in all the excitement.

Arthur I thought about stealing things just to make it a nightmare for continuity. Like the Tardis floor…

Karen And Arthur and I actually got the same leaving present, which was two massive pictures of ourselves. It’s awkward because I don’t know what to do with it. It kind of dominates a room.

Has your life really changed?

Matt Your life changes categorically when you join Doctor Who. I’ve tried to tell this to the new companion Jenna-Louise Coleman, but it’s quite a hard thing to explain. Alex Kingston [who plays River Song] tried to explain it to me and Karen. We were in a restaurant in Cardiff a week before we started, and Alex said, “You have no idea, you two.” You won’t be able to sit in this restaurant in the same way, for a start.

Karen She was sitting there shaking her head and we said, “What are you talking about?” Then it happened and now we definitely understand.

Matt It’s just one of those things. Some bits are great and some bits are not so great. But that’s how it goes. I enjoy playing the part and it’s a product of being in the show. That’s the deal.

Karen I feel like I’ve grown up and that I can now handle situations a bit better because I’m a more assertive person. I’m starting to feel more like the person that I want to be.

And how is the new companion getting on?

Matt The show is so much about dealing with Steven’s writing, having an instinct for the tone and pace. And Jenna nailed that tone of fear and adventure. We did the auditions down in the bowels of the BBC and it was meant to be top secret, which is ridiculous because we’d been going for four hours when we heard a cough behind a partition. And there was this security guard with his feet up and we said to him, “Man, do you know what this is?” And he was like, “What?” So it wasn’t that secret. But I did phone the Daleks in and said, “I need a favour, boys…”

Karen I’ve met Jenna and we get on really well. And I’ve been texting her bits and bobs about Matt, but what I wrote is a secret. That’s the code of the companion. I didn’t offer her any advice though because I want her to have the experience for herself. I didn’t want to plant any preconceptions in her head.

So, what about the Doctor’s 50th anniversary next year?

Matt We want to make it as big and bold and as brilliant as we can because, we hope, it can be one of the monumental bits of TV history. But I doubt there’ll be a regeneration…

Karen I decided there’d be no cameo returns after I leave. I want the impact of the end of the Pond era to remain strong. I don’t want to spoil it by coming back a few episodes later to say hello.

Arthur Yeah, I like the idea of going out with a big bang and being able to say, “Well, that was that.” And then I can watch it in future without knowing what’s going to happen.

Matt Steven will tease you all right to the end. Because that’s what he does to me.

Matt, is it true you were nearly in Sherlock?

Matt Well, I thought my audition for Watson was very good. But clearly not good enough! Basically they looked at it and went, “He’s not Watson. It’d be like having two Sherlocks in the room.” But Martin Freeman was born to play that part. And rightly so, thank the stars. I wasn’t destined for Watson but I met Steven Moffat, who said: “He’d be quite a good Doctor Who…”

Series 7 of Doctor Who starts tonight at 7:20pm on BBC1

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