When you're surrounded by friends and exes, there's a whole lot of stuff that starts crawling out. But however serious and traumatic those experiences may be to the participant, to the onlooker they're hilarious.

What is immutable about Sherlock Holmes? He favors reason over emotion, but actually underneath that, there is a lot of emotion going on. You can't suddenly make him ordinary because he would hate that. He's not suddenly going to be somebody else.

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

You take this cold, remarkable, difficult, dangerous, borderline psychopath man, and you wonder what might have happened to him had he not met his best friend, a friend that no one would have put him with, this solid, dependable, brave, big-hearted war hero. I think people fall in love, not with Sherlock Holmes or Dr. Watson, but with their friendship. I think it is the most famous friendship in fiction, without a doubt.

I know this is going to sound very self-serving, and I apologize for it, but if you can write comedy, you can pretty much write anything, because it's the hardest. It's the most technically demanding, the most precisely evaluated form of writing. People know if it works or not. There's a big button marked 'fail,' and that's when nobody laughs.

Fascinatingly confident, rude people are great.

Every episode [in a TV series] is a challenge, and what's challenging in most episodes is the monster. You're always a heartbeat from the monster looking ridiculous. You really have to work so hard to make them not look like ridiculous when they turn up on the set.