Sherlock: 6 Reasons It Needs To End (And 4 Reasons It Should Come Back)

4. Sherlock's Character Arc Is Complete

Benedict Cumberbatch's Sherlock has undergone quite a dramatic character development over the past four seasons. He began the show as a self-confessed high-functioning sociopath, someone so callous and isolated from humanity that his colleagues on the police force thought him capable of being a serial killer.

Come the end of season four, however, he's a crusading dragon-slayer - someone human enough to offer to kill himself in order to save the life of his brother and best friend, and compassionate enough to offer forgiveness to his murderous misguided sister. In short, he has completed his journey to fully-fledged hero.

So where would the character go next? Showrunners Steven Moffat and Mark Gatiss have said that, looking back, these seasons form 'chapter one' of the usual Sherlock Holmes story and, if the show was to return, Sherlock would be much closer to the wiser, politer detective of Doyle's stories.

Really, though, would that be as interesting as the more volatile, ruder Sherlock we have come to love? Shouldn't the show just call it quits now if the main character has nowhere else to go?