The idea came before the casting. I thought ‘And she’ll be a woman’ then having said that, I then got lost for several months going ‘and what does that mean? So what?’ That’s exactly the kind of gimmick I’m always saying you shouldn’t do, so what does it mean? I’ve always said in the past we cast the person, you cast an individual, you don’t cast a gender, that’s bananas – as she would say.

Fortunately, I was grumping around the office one day and I found a list for another part and Michelle Gomez was on the list and I thought ‘oh my God that would be brilliant, Michelle is the perfect person, I can write it now. I know what she’s going to be like’, only to discover they’d already offered her the other part. Fortunately she turned it down because she was busy – you assume when someone turns a part down because they’re busy that they’re lying and just don’t want to work with you, because I know her and that would be a reasonable reaction – but then she sent me an email about a week later that said ‘I’m so horrified I had to turn it down, I really really want to be in Doctor Who. If you ever have a part for a razor-cheekboned villainess…’ and I thought right, that’s so happening. I wouldn’t even discuss anybody else. It had to be Michelle, and I think, going by the response, that was right.

That made sense of it, what really mattered is that we got an arch-enemy performance that I think matches the amazing Roger Delgado and John Simm, those are stellar performances and that’s another one that’s every bit as good. She’s alarming and she’s scary, she’s extremely funny, and you still vaguely side with her when she kills harmless, likeable, defenceless people.

On why fan avatar Osgood had to die in Death In Heaven:

I was aware that the Master as a character gets cuddly very fast, even the Roger Delgado version is one of the chums quite quickly. I thought if we’re going to bring that character back, she’s got to kill somebody you really like in the most merciless, horrific way and be really horrible about it. You’ve got to really lay it on the line that she’s a truly awful, evil person, otherwise she just becomes a sort of comedy alternative Doctor who’s a little bit naughty. You could say River Song was that in a way, but you’ve got to say no, this person is a really evil person. I don’t know who the fan base are identifying with so I don’t sit around thinking ‘I’ll lure them into… and then kill that character!’ That would be rude, and I wouldn’t do it. It’s someone who really wanted to travel in the TARDIS and then never got the chance because she got offed by the ex. It’s not a sinister plan.