 Rupert Graves was cast as DI Greg Lestrade . The writers referred to the character as " Inspector Lestrade " during development until Gatiss realised that in contemporary England the character would have the title " Detective Inspector " . Moffat and Gatiss pointed out that Lestrade does not appear often in the stories and is quite inconsistently portrayed in them . They decided to go with the version that appeared in " The Six Napoleons " : a man who is frustrated by Holmes but admires him , and whom Holmes considers as the best person at Scotland Yard . Several candidates took a comedic tack in their auditions , but the creative team preferred the gravitas that Graves brought to the role . His first name is revealed to be Greg in " The Hounds of Baskerville " . 
