Kathy Nightingale: What's good about sad? Sally Sparrow: It's happy for deep people.

Cinema is so slow and boring compared to television.

Fascinatingly confident, rude people are great.

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.

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.

There's something that doesn't make sense. Let's go and poke it with a stick.

Writing for adults often means just increasing the swearing - but find an alternative to swearing and you've probably got a better line.