Steven Moffat: We like to keep Sherlock fans wanting more

Since the detective series, starring Benedict Cumberbatch and Martin Freeman, first aired in 2010 there have been just three, triple-episode series.

Steven, who co-writes the show with Mark Gatiss, said: “The appetite for Sherlock is wonderful.

“I feel slightly guilty that we may have exacerbated the appetite through starvation because we make so few of them over so much time. But it’s incredibly rewarding that each time we come back it’s so rapturously received.”

But the writer and producer revealed if they had made more episodes of the hit show, they probably would not be able to persuade Benedict and Martin to stay on as Sherlock and Watson.

Steven said: “It makes it last longer, that’s for sure. If we’d done it at the normal rate, which would be six to 12 every year or every two years, we’d be finished by now and we’d never get hold of Benedict and Martin again.

“So it’s certainly kept it going, and it’s nice that we don’t wear it all out. It’s still quite fresh even though it’s a few years old now.”

Steven also promised Doctor Who fans they can expect more mayhem from Missy The Master when Michelle Gomez returns in the new series of the sci-fi show.

He said: “Michelle is shooting more or less right now for the opening two-parter.

“Michelle was such a hit. And that was such a big thing to do, almost a tricky thing to say ‘are people going to go for this beloved yet hated character when we change the gender?’. But they didn’t blink, they’re perfectly happy.”

He said of the new series: “There are certainly surprises, but she’s still the same evil Missy she was last time.”