Benedict Cumberbatch and Martin Freeman outside 221b Baker Street BBC

Sherlock co-creator and producer Steven Moffat has spoke out about the show's series 4 return.

In an interview with IGN the writer said: "If people have to wait two years, they'll have to wait two years."

He also likened the hit detective show to James Bond, a comparison not lost on anyone who saw the first episode of the show's third series.

"I have no idea," he said when asked about when the show might return. "Sue's working on the schedules right now and I just started with [Peter] Capaldi on the new series of Doctor Who.

"You know, we'll do what we can, but with no sacrifice in quality - that's the thing. If people have to wait two years, they'll have to wait two years. When's the next James Bond film?

"You know, it's not that kind of show that turns up all the time. It's just not. But the good news is, that probably means it will turn up sporadically for a very, very long while."

Fans of the BBC drama have had to wait two years for each sequel series so far, and there's no reason they won't have to again, though it is understood that the Beeb are as eager as fans to get the show back sooner rather than later.