The fourth season of Sherlock has all-too-quickly concluded, leaving fans reeling over numerous unanswered questions and an unquenched thirst for more mystery-solving.

Unfortunately, a fifth season of the BBC drama is all but certain, mainly thanks to Benedict Cumberbatch and Martin Freeman’s hugely busy schedules.

Despite both actors saying they would like to return, there’s an increasing amount of doubt over season five. So, what have the show runners said so far?

Steven Moffat, one of the show’s creators and writer, said at a recent screening: “If this is the last time - and I’m not planning on it to be, but it might be - it is possible that we could end it.”

He continued: “We couldn’t have it ended it on any previous series because they always ended on walloping, great cliffhangers."

Sherlock season 4 in pictures Show all 7 1 /7 Sherlock season 4 in pictures Sherlock season 4 in pictures Mark Gatiss and Benedict Cumberbatch in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: Mycroft Holmes (MARK GATISS) and Sherlock Holmes (BENEDICT CUMBERBATCH) Copyright: Hartswood Films 2016. Sherlock season 4 in pictures Una Stubbs as Mrs Hudson in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: Mrs Hudson (UNA STUBBS) Copyright: Hartswood Films 2016 Sherlock season 4 in pictures Mark Gatiss in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: Mycroft Holmes (MARK GATISS) Copyright: Hartswood Films 2016. Sherlock season 4 in pictures Toby Jones in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: Culverton Smith (TOBY JONES) Copyright: Hartswood Films 2016. Sherlock season 4 in pictures Martin Freeman in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: John Watson (MARTIN FREEMAN) Copyright: Hartswood Films 2016. Sherlock season 4 in pictures Martin Freeman, Amanda Abbington, and Benedict Cumberbatch in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: Behind-the-scenes filming 'Sherlock' Season 4. John Watson (MARTIN FREEMAN), Mary Watson (AMANDA ABBINGTON) and Sherlock Holmes (BENEDICT CUMBERBATCH) Copyright: Hartswood Films 2016. Sherlock season 4 in pictures Amanda Abbington, Benedict Cumberbatch, and Martin Freeman in Sherlock Sherlock, Season 4 premieres January 1, 2017 on MASTERPIECE onÂ PBS. Picture shows: Mary Watson (AMANDA ABBINGTON), Sherlock Holmes (BENEDICT CUMBERBATCH) and John Watson (MARTIN FREEMAN) Hartswood Films 2016

Previously, Moffat has hinted season four could be the end of Sherlock but has consistently remained optimistic, saying back in July: “I would be moderately surprised if this was the last time we ever made this show. But it absolutely could be.”

Benedict Cumberbatch, meanwhile, has previously gone out of his way to rubbish rumours the show would not be returning. Speaking to AP, he said: "We love doing the show and all I'll say about it is that we're all very busy… For now, it's not going to happen again at the same regularity that it has been happening.”

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More optimistically, he added: "But we'll see, we'll never say never and when it's right, and if it's right, we'll do more.”

The most pessimistic member of the cast remains Martin Freeman, who told Radio Times: "Truly, I don't know how long it will go on. But these days we want everything yesterday, we're never sated, we want what's next, what's next, what's next. And I think, 'Wow, there's hours of telly you haven't watched yet,' you know? So let's just enjoy them.”

Even with all the uncertainty, the BBC remain as optimistic as ever, with RT claiming a BBC source believes another series definitely won’t take place next January but is “reasonably hopeful” regarding a new series the following year.