Cast your mind back to last Sunday and you’ll recall Sherlock and Mycroft Holmes and John Watson almost met a very sticky end thanks to a drone rigged with explosives that secret Holmes sister Eurus flew into 221b Baker Street. Logic suggests that the Sherlock team were never going to kill off their leading trio, but it was still a tense moment watching them plot their escape from near-certain death although personally we were more worried about the fate of hoovering rockstar Mrs Hudson downstairs… It was down to the special effects team to cook up exactly how such an explosive twist would reach our screens and since the episode aired, they’ve been sharing the tricks of their trade.