Sherlock has been a barnstorming success, and it’s not often you get to hand that phrase out. It might not seem like a surprise to us schmucks, but the show’s writer and producer, Steven Moffat, can’t believe the BBC drama is bringing in the kind of numbers it is.

Sherlock Season 3 cast

Moffat says in a statement: "It isn't supposed to be like this. Sherlock began life as a surprise hit, and now in its third series, it's rating higher than ever." The third and final installment of the current series, His Last Vow, pulled in 8.8million viewers, which equated to 32.1% audience share.

"This show, which we all thought would be our vanity project destined for 3 million in the ratings and possibly an award from an obscure European festival, has become a barnstorming international phenomenon,” explained Moffat, according to The Mirror.

"If I live to be a very old man, I might be able to explain how any of that happened - drop me a line in about 40 years, I'll do my best. Till then, on behalf of Mark and [producer] Sue [Vertue] and myself - who started all this, not so very long ago - thank you all for the very best of times!"

The three-part third season of Sherlock saw the mercurial detective cheat mortality, give the best ‘best man’s speech’ of all time, and see one of his deadliest foes come back for the finale. It was a strange run, consisting of three movie-like episodes, but it certainly seems to have chimed in with the fans.

As for more, fans will have to wait until Sherlock’s stars can figure out a time to work together, considering their increasingly hectic calendars. "Everyone is very keen to do more, but we have accidentally cast the 2 most successful actors in the world & schedules are tight," Moffat and co-creator Mark Gatiss said in a Q&A.