It sounds like the kind of joke you pull out of a Christmas cracker...
Q: "What's Sherlock Holmes's favourite party game?"
A: "Give Us a Clue."
For younger viewers (or younger than me, anyway) Give Us a Clue was televised charades (yes, really) with Una Stubbs, who now plays Sherlock's landlady Mrs Hudson, leading one team of celebrity guessers while Lionel Blair took charge of their opponents.
So it's rather satisfying to hear that while Benedict Cumberbatch was shooting Sherlock's lengthy best man's speech in wedding episode The Sign of Three, his co-stars were relaxing by playing charades.
"I loved doing the wedding," said Martin Freeman who, as John Watson, was marrying his real-life partner Amanda Abbington, aka Mary Morstan. "It was a beautiful few days on a lovely set, with lovely people and we got to watch Ben do a monologue... We were just playing games between takes while he was having a nervous breakdown."
"We played give us a clue with Una Stubbs," confirmed Abbington, speaking at the iTunes launch of Sherlock series three.
Despite missing out on the games, Cumberbatch said he'd had "great fun" filming the "weird one man show".
Just possibly not quite as much fun as his co-stars...
Sherlock Series 1–3 Deluxe Edition on iTunes