I was rewatching The Great Game (S1E3) and you know that scene after the whole Janus Cars business and there’s Lestrade, John and Sherlock on this garage place and then Sherlock and John just walk away and the lights are turned off as they walk away…
It just came to me….did they just…leave Lestrade alone in the dark?!
Mycroft was probably just waiting for John and Sherlock to leave…