Karen Gillan has promised that Saturday’s “disturbing” finale, A Good Man Goes to War, is chock-a-block with “shocks and twists and turns”, in particular the “huge revelation” about River Song.

Speaking to What’s on TV (spoilers!), she said: “This is the episode where it’s finally revealed from way back when we met her with David Tennant. It’s a huge pay off and I didn’t see it coming. I was really, really shocked and it was worth investing all that time into it in the past.”

The actress also spoke in favour of the series split. “It means it lasts longer, which is always good,” she admitted. “We’re also going to end on such a huge revelation that I think everyone will need the whole summer to digest it.”

A Good Man Goes to War premieres on Saturday at 6:40pm on BBC One/BBC One HD.