"It was beyond all of our wildest dreams', says Martin, talking about the response to the first series of Sherlock.
"We hoped it would be well-received and as popular with viewers as it was with us. We loved making it and are very proud of it, but beyond that it's out of your control as to how people will view it, so the response was great."
A large part of the success of the show, is the great partnership and relationship between Sherlock and John Watson, from their first meeting to sharing a flat together at 221b Baker Street, Martin goes on to explain how the relationship has evolved and what to expect in series two.
"By the end of the first series you saw John and Sherlock's relationship moving on, John went from being merely 'agog' at everything Sherlock did to being just miffed at some of his actions. That takes a step further in the new series and I would say it is definitely a partnership now, with Sherlock being the main thrust, but John is only half a step behind, as opposed to six steps behind."
John Watson, famously is written as a bit of a ladies man, so what will he make of Sherlock's love interest in episode one:
"John thinks Sherlock would be much healthier if he had a relationship with a human being as opposed to a theory or something. John in the interim, according to the writers, he's had a number of girlfriends, so I think he'd like Sherlock to do the same. I think it makes Sherlock more human in John's eyes."
In terms of what the audience can expect from John Watson this series, Martin explains:
"Well, John is not about to start doing deductions, but you kind of need John there, what he brings to 'the game' isn't the same as Sherlock, but it's kind of useful doing, as Mycroft says with disdain, 'the legwork'. John can do different legwork to Sherlock, but he'll do it all the same. It's pretty much more of that really, I mean there's only so much you can develop John's role in the deduction because then it's not Sherlock anymore. it has to be primarily about him, and that's the only way to do it, with John as backup.
"All that I require, as an actor, and as an audience, is that it's good backup, that it's interesting and it's three-dimensional, because otherwise I can't see the point of being here, and I certainly wouldn't be doing it if it wasn't interesting."
Martin describes one of his most memorable moments about Sherlock was arriving on set for the first time:
"I remember the first time I went on set, there was this beautiful slightly shambling, slightly chaotic, but classically designed room, that you can believe is a Victorian room. There are a lot of houses in London that look a bit eccentric, they're a mish-mash of designs and periods, and it's completely believable."
In terms of what it is about the Sherlock and John relationship that people love so much, Martin suggests:
"I think people just like seeing friendship. I think people like seeing people who just drive each other up the wall, but at same time, can't live without each other. You see it in Waiting For Godot and Steptoe And Son, that's everything, especially involving two blokes who want to kill each other, but ultimately, where else are they going to go?"