SPOILERS: DO NOT READ IF YOU HAVE NOT SEEN SHERLOCK SERIES 4 EPISODE 3 THE FINAL PROBLEM
So, Sherlock series four is over – but what next?
At the end of season four finale The Final Problem, Benedict Cumberbatch and Martin Freeman’s heroes are seen back in their rooms at 221B Baker Street solving crimes.
It's a moving montage, featuring a voiceover from Amanda Abbington as John's late wife Mary Morstan and showing the two of them doing what they do best.
The pair are also shown exiting a building marked Rathbone Place – a homage to the great actor Basil Rathbone who played Sherlock Holmes in the movie versions in the 1930s and 1940s.
And, according to the show's writers Mark Gatiss and Steven Moffat, events at the end of The Final Problem could be just the beginning...
If there is to be a series five – and it appears that all parties are keen to make that happen at some point in the future – then it will be from this starting point, according to the writers, who have indicated that Benedict Cumberbatch’s Holmes has now discovered the humanity that it is at the heart of the detective’s brilliance.
Gatiss explained: “Our original intention of the series was to go back to the beginning and see them as younger men and… restore it to its factory settings. But I think what’s actually happened is that we have now done the story of how the Sherlock Homes and Doctor Watson that we have always known, how they became those men. It’s actually really a backstory.
“The reason we [ended with] Rathbone Place is that, actually, if we do come back – and we would love to come back – we could absolutely very easily start with a knock at the door and Sherlock saying to John 'Do you want to come out and play?'. They have become the two heroes that we always knew them to be."
Moffat added: “I suppose it’s that Sherlock now finally understands that’s he’s stronger and smarter than Mycroft in a way. But not because he is actually smarter – he’s less smart – but because his emotions, his connections to other human beings, the wisdom he has gained from his connections he has made in the world, make him stronger.
"He sees that, partly because the extreme of [his sister] Eurus who has no connection to anything, is just pure brain, not understanding anything about what it is to be human. [This] makes him realise everything he has worked towards, everything he has tried to get away from himself and deny about himself, is what makes him the strongest.
“He isn’t as smart as Eurus, he isn’t as smart as Mycroft but he is always going to win against them because he is better and stronger. That is him becoming the Sherlock Holmes of Basil Rathbone and [fellow Holmes actor] Jeremy Brett, the one we’re used to, the wise old man… who is still terrifying and still cold but has a heart that you never doubt."
As to whether there will be a fifth series, Moffat added: “If this was the last time – we’re not planning it, but it might be, it’s possible – we could end it there. We couldn’t have ended it on any of the previous series because they always ended up with whopping great cliffhangers."
He said a fifth series would see Sherlock and John – no surprises here – "solving crimes".
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Moffat also revealed to RadioTimes.com that he and Gatiss toyed with the idea of flashing the line “The Beginning” across the screen at the end of The Final Problem.
But while it accords with the theme of the episode, he said that in the end they decided it would have been “too cheesy”.
And, of course, it would have meant a few hundred more questions from the audience about series five...