On the other hand [making a string of one-off episodes], there's a real freedom, because you're kind of reinventing the show every week.

Whenever anything nice happens in the world I always expect something appalling to happen immediately afterwards.

In a weird way, when everyone's feeling that the world's going to hell in a hand basket, I kind of relax a little more because I often feel like that.

"Be Right Back," in which Hayley Atwell brings Domhnall Gleeson back from the dead using his social-media profile, sprang out of an unrelated conversation. Other stories you thrash away at for weeks and weeks.

Seriously, if I switched on the TV and they were showing live footage of an army of fire-breathing pterodactyls machine-gunning people to death on the streets of London right outside my door, I'd be horrified, but not entirely surprised, nor any more scared than I already am. I'd probably just shrug and wait for them to smash the door down. We're so screwed, I don't even know what to worry about first.

While I was thinking about that, the military, I read a book called On Killing, about the obstacles people have to pulling the trigger in combat. So sometimes you just absorb all this stuff without realizing you were doing research.

Being slagged off is good for you. It thickens the skin and strengthens the backbone.