“I play Caretaker Two,” David [Tennant] says proudly. “It’s very hard not to get excited. I would kill to do more of these.” David is a fully-fledged, card-carrying Doctor Who fan. “My granny even knitted me a long Tom Baker scarf. And a cricket jumper. I used to jump around the back garden making up my own stories. As I got older, I’d make up my own seasons.”

In the back garden?

“Yeah – casting myself in all the parts. Oh God, how embarrassing.”