There are "plenty of surprises in store for series three" of Sherlock, according to BBC1's official Twitter account – not least, that Benedict Cumberbatch and Martin Freeman chose to don flat caps for the first table read-through...

The stars are shown wearing the headgear (and not a deerstalker in sight) along with ridiculous grins in a photo from the initial rehearsals. Even stranger is the fact that Freeman also has what appear to be grapes in his eyes. Why? That's a mystery we think even the great detective would struggle to solve...

Sherlock series three begins filming next Monday, 18 March, and is set to air in the autumn.