Two massive BBC1 shows, Sherlock and Doctor Who, return to the screen this year. And there will be high expectations of the man behind them both, writer Steven Moffat.

As the successor to Russell T Davies at the helm of Doctor Who, Moffat had already become one of the few British TV writers to acquire the kind of recognition usually reserved for those on screen. But last summer's Sherlock, which Moffat co-wrote with Mark Gatiss, propelled him to a whole new level. "I've found myself in this situation and, let's be honest, I won't be in it for that long," Moffat says. "Nobody in their right minds could have expected this. It's ridiculous. I can't think of anyone having this much fun in TV at the moment." Moffat's writing sparkles with playful asides and smart one-liners. "I particularly like writing the Doctor. He's such a fun character, he's so mad," he says, with glee. But surely the bigger his shows become, the more pressure there is to live up to fans' expectations? "Pressure," he says, "is when everyone hates the show and you still have to write the second series!"

He remains tight-lipped about what lies in store. "You can have three words to work from," he laughs. "Adler, Hound, Reichenbach. Those are your clues."

When it comes to Doctor Who, Moffat admits that it's "entirely impossible" to escape the brouhaha that surrounds the show. "But it's not inhibiting at all – I love Doctor Who, so I love writing it. You are aware at times of the importance of Doctor Who to the BBC, but the remarkable thing about the audience isn't so much its size, which of course is considerable, but the passion of the fans."

This year the episodes are to be split into two separate chunks, with seven in the spring, and six in the autumn, when Sherlock will also be returning to our TVs. It is not unlikely that Moffat will see his shows vying for accolades on BBC1.

Praise, however, does not need to come in grand form. The greatest compliment, Moffat says, "is if I mention the show to someone and their face lights up and all they can talk about is how much they adore it."