Doctor Who: it’s back is promising to be the scariest and darkest of the TV series yet, with one of the show’s four main characters to die.

But the question is, which one?

Show runner Steven Moffat dropped the ‘spoiler’ bomb, by revealling that one of four characters – the Doctor, played by Matt Smith, his companion Amy Pond (Karen Gillan), her husband Rory Williams (Arthur Davill) or mysterious fellow time traveller River Song, played by former ER star Alex Kingston – will meet their death.

“We’re not lying, we’re not cheating. One of those four people is going to die,” Moffat told the new issue of Doctor Who magazine.

“The Doctor’s darkest hour is coming. Shows like Doctor Who should have big colourful, memorable moments that make you go, ‘What the hell?’ Well, this is one of them.

“It’s hard to create shock in Doctor Who when we’ve already blown up the universe a couple of times. What do you do next?”

Moffat said the first two episodes of the new series – which feature a mystery alien species known as the Silents – is the scariest opener to any Doctor Who series yet.

“You put the jokes in for the adults, and you make it scary to appeal to children. They absolutely rank the best Doctor Who episodes in order of frighteningness.”

The opening two-part episode, is set in 1960s America and features the moon landings, Richard Nixon in the White House, Area 51 and an alien race with a unique USP.

Fans might assume, since Smith and Gillan signed up for the duration of the series, they’re not on the chopping block, but what’s to say they haven’t travelled back in time and changed their mind?

The cliffhanger is expected to generate plenty of expectation around Doctor Who’s return to BBC1 on Easter Saturday, 23 April.

It is the sixth series since the Saturday teatime favourite returned in 2005 after a 16-year absence.

Moffat, one of the creative powerhouses behind BBC1’s acclaimed re-imagining of Sherlock Holmes, has promised to double the number of “event episodes” in the new run.

“You are going to get several cliffhangers and a couple of real belters,” said Moffat. “If you run for 13 weeks [viewers] can start to feel like you can miss one and it would be okay. We want to stop that feeling.”

While there were plenty of plaudits for Smith – who at 26 was the youngest actor to be given the role two seasons ago since it began in 1963 – there was a mixed reception for last year’s series, the first overseen by Moffat, with ratings down year on year.

The new series will feature guest appearances from Downton Abbey star Hugh Bonneville, David Walliams, James Corden, Lily Cole, and the voice of Michael Sheen, as well as the return of one of the doctor’s most enduring foes, the Cybermen.

It will be split into two, with seven episodes running until June before it returns with another six episodes in the autumn.

Moffat has refused to reveal weather this series will see the return of the daleks.

“That’s the excitement. I’m not telling you.”

BBC1 controller Danny Cohen, described Doctor Who as “unique and brilliant … world class science fiction and a testament to the stars and the people who make it”.