6. Molly Happy Returns

Molly Hooper was originally created as a one-note character for the mortuary scenes in A Study in Pink. However, everyone was so taken with Louise Brealey that Mofftiss broke their one rule for Sherlock – that all the major characters would be taken from the original Conan Doyle stories – and made her into, yep, a major character.

7. What is hidden under that umbrella?

Mark Gatiss has repeatedly tried to persuade Moffat that Mycroft should have gadgets and tricks hidden inside his umbrella, but to date has always failed. Maybe one day, Mark…

8. The Sherlock work-out

Benedict Cumberbatch has some strict rules for himself when preparing to play Sherlock. He stops drinking and smoking during filming and practises swimming and Bikram yoga sessions, which take place in a sauna (a place which, coincidentally, Holmes enjoys visiting in the canon).

9. The Holmes truth

In The Great Game, there was initially a scene which explained the reason behind Sherlock and Mycroft’s sibling rivalry – Mycroft blamed Sherlock for causing an incident that strained the family when they were boys. However it was cut as Moffat and Gatiss decided it would be better to keep it a secret.

10. More-iarty

Moriarty was initially only going to feature in The Great Game as Jim from IT but Mofftiss were so impressed with Andrew Scott’s performance that they quickly inserted the swimming pool scene at the episode’s end. The exchange between Sherlock and Moriarty here was originally written for Scott’s audition for the role.

Is there a fascinating behind-the-scenes fact from Series One that we have missed? Leave it in the comments!