The Version Interview... Benedict Cumberbatch on Sherlock series 4

Sherlock returns to BBC One with three brand-new feature length episodes, promising laughter, tears, shocks, surprises and extraordinary cases.

The eagerly anticipated fourth series, produced by Hartswood Films, begins with the nation’s favourite detective, the mercurial Sherlock Holmes, back once more on British soil, as Doctor Watson and his wife, Mary, prepare for their biggest ever challenge - becoming parents for the first time.

Benedict Cumberbatch and Martin Freeman reprise their iconic roles as Sherlock Holmes and Doctor Watson in the hit drama written and created by Steven Moffat and Mark Gatiss, and inspired by the works of Sir Arthur Conan Doyle.

How does it feel to put Sherlock’s famous coat back on after being in Victorian costume?

Its lovely putting the famed coat back on again, as opposed to the starched collar and the morning suit, but at the same time, we were filming in the middle of summer so it was quite hot every time I put on the coat! Its part of who he is, part of his kit and his armour.

How do we find Sherlock, John and Mary at the start of series four?

There are a lot of new things going on, for example there’s a baby! So parenting responsibilities have kicked in for the super sleuths! Childcare is never easy but it gets even more complicated when crime’s involved.

John and Mary are new parents, how does Sherlock feel about that?

I think Sherlock feels very protective towards them as a family, but he’s not a natural or a figure of authority when it comes to a new-born. I hope my skills and interaction with my own are a little bit more engaged than his are! He’s seemingly indifferent which is comic at times but it’s all underpinned with a deep love and he’s a guardian angel really.

How did you go about creating your version of Sherlock Holmes?

Sherlock isn’t just Sherlock, he was a baby, then a child, then an adolescent, then a young adult, and then the 30 year old that you met in Series One, Episode One. We know he’s got a brother called Mycroft and parents but what the hell was his childhood really like? I wanted to know all that information very early on because you’re playing the most adapted and greatest fictional detective of all time. You need to have a back story to work off as an actor because what are you doing other than emulating certain airs and graces and mannerisms. What I try to do is underpin all those decisions with an informed understanding of who my character is.

What is so appealing about playing the character of Sherlock?

Whatever scale I’m working on as an actor it’s about telling interesting stories and just losing myself in an experience. There’s a degree of comfort in coming back to something you know, it’s nice getting the band back together and playing certain aspects of him. I don’t return to roles very much, even this has only been twelve episodes and one special so far, we haven’t made that many.

The scale of Sherlock is always, in ambition, as big as anything on any other kind of format. The final rendering of what we produce is very filmic and very high quality and that’s saying something because it’s not only low budget when it comes to what designers in every department have to work with in comparison to a big film but it’s also the amount of time we have to perfect it in.

They say never work with children or animals, in series four you work with both, how did you find it?

We had an interesting dog in the first episode. He was very sweet but was a bit afraid of being in the centre of town, afraid of too many people and not great on hard surfaces. We were in Borough Market, with lots of people around, on concrete and tarmac. Cut to Amanda literally pulling a bloodhound around London who was supposed to pull her around London. That was fun.

The babies have been pretty amazing, I’m a father and I know how difficult it is to get anything in tune with a baby’s schedule. It keeps you in the moment and it stops you being precious about your work. I love those elements that make it more difficult.

How much of Sherlock’s temperament is driven by the apparent inadequacies of others rather than his own desire for perfection?

Oddly, I think Sherlock’s temperament is more shaped by the fact that he is human and trying to be superhuman. The amount of stuff that we call polite civilisation is a huge distraction to this man who has to think on an unparalled level of complexities. It’s not really that the world is stupid it’s just that for him to be clever he has to really drown out a lot of noise and what he permanently gets surprised by, and what I think is his real weakness, is sometimes not seeing what’s right in front of him. His blind spot is the very thing that he purposely turns his head from in order to be as good as he is as a sleuth. So it’s a complex relationship he has with the world. He needs it to be that way in order to conquer it but at the same time the way he engages with it often blinds him to the most obvious. That’s great from a story point of view because people don’t see things because he doesn’t see them. His stupidity is also the world’s brilliance which is why there are things, people, and events, which overtake him. He’s not unhuman, he is human and he is fallible.

Sherlock. 9pm, New Year's Day, BBC One.9pm,