The trouble with a series as it gets older is it can feel like a tradition, and tradition is the enemy of suspense, and it's the enemy of comedy. It's the enemy of everything, really. So you have to shake it up.

Never knowingly be serious. Rule 27.

There’s this issue you’re not allowed to discuss: that women are needy. Men can go for longer, more happily, without women. That’s the truth. We don’t, as little boys, play at being married - we try to avoid it for as long as possible. Meanwhile women are out there hunting for husbands.

We're thrilled to have Maisie Williams joining us on Doctor Who. It's not possible to say too much about who or what she's playing, but she is going to challenge the Doctor in very unexpected ways. This time he might just be out of his depth, and we know Maisie is going to give him exactly the right sort of hell.

I write the kind of stuff I'd like to watch.

Everybody knows that everybody dies. But not every day. Not today. Some days are special. Some days are so, so blessed. Some days, nobody dies at all. Now and then, every once in a very long while, every day in a million days, when the wind stands fair and the Doctor comes to call, everybody lives.

Sherlock Holmes becomes more human and more adept at fitting in with a lot of people, but he remains separate from the human race because he finds that a better place to observe that from. He stays on the mountain top because there, he can see clearly.