Martin Freeman (The Office) stars as Dr John Watson in Sherlock, BBC One’s new update of Arthur Conan Doyle’s classic detective, set in present-day London.

Dr John Watson has been through hard times and seen bad things. An army doctor just invalided home from military service in Afghanistan, he’s a lost soul, adrift in London, until a mutual friend introduces him to a strange young man called Sherlock.

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How did you first feel about the prospect of an updated portrayal of Sherlock Holmes?

“When I heard they were updating Sherlock, I thought it might be a bit anachronistic for its own sake. I was sent the script and by about the end of the fourth page I just thought: ‘This is genuinely brilliant’. It was probably the best script I’d read for ages, it’s fantastically well written, regardless of when it’s set.”

Dr John Watson has often been represented as Holmes’ sometimes “bumbling” sidekick – what’s your portrayal of the character like?

“In this version, Sherlock and Dr John Watson are both evenly weighed. John is not just a side-kick, he has a really good role to play. Every actor wants to play someone three dimensional and this is as close as you get. Part of what attracted me to this version of Sherlock is, as in the original Conan Doyle stories, Watson is the story-teller. You’re experiencing these adventures through Watson’s eyes and through Watson’s words. My character writes up all the cases in his blog, just as Watson wrote the cases that formed the original books.

“I saw no reason to see him as anything other than very able. He’s a military doctor, just returned from Afghanistan – he’s somebody who can handle himself and makes life or death decisions on a daily basis.”

What’s the dynamic like between Watson and Holmes?

“Sherlock likes the game of it, whereas John is, at first, horrified by how Sherlock treats a dead body as a game. Sherlock wants to be the cleverest person in the world – he’s got a real ego. “Sherlock is ‘un-socialised’ and I think John likes that about him, but it also infuriates him. I think he’s flattered to be the person who Sherlock wants to hang around with, though.”

Did you enjoy working with Benedict Cumberbatch, who plays Sherlock?

“I’d never met Benedict, but I’d liked his work as a viewer. Benedict looks like you’d imagine Sherlock Holmes should be and he can really act. It was really nice to watch a really good actor in the driving seat. We found working together quite easy – we seemed to gel and we kind of understand where one another is coming from. Chemistry-wise, it felt good.”

How have co-creators and writers Mark Gatiss and Steven Moffat updated the stories?

“We have two genuinely fantastic writers at the helm. They also happen to be big, big ‘Doyle-heads’. Clearly they love Conan Doyle, so they want to facilitate it, it’s not like they are going to kick out stuff to make it a bit more hip, more Skins or The Inbetweeners. They are very respectful of Conan Doyle work, without it being dry. Steven and Mark are very good at incorporating plot and character; one isn’t sacrificed for the other.”

What would you say to people who question the idea of bringing Sherlock Holmes into the present day?

“I think it really stands up. Steven’s rationale was that we update Ian Fleming with Bond all the time – we’re not seeing Daniel Craig in the Fifties. Arthur Conan Doyle’s stories are certainly rich enough to do that with. It’s written by huge Conan Doyle fans who really love this stuff as well as being very enjoyable so there should be a few boxes ticked for the Doyle-nuts, too!”