Speaking about River’s identity to Doctor Who Magazine in an interview to be pubished in the next issue, Moffat teases: “An instalment is revealed [this series]. But there are a fair number of layers to this.”

In another ambiguous teaser quote from the interview posted by the magazine on Twitter, perhaps discussing River and the Doctor’s relationship, Moffat says: “I think it’s the ultimate no-win, tragic love story…”

Series 6 begins on Saturday 23rd April with ‘The Impossible Astronaut’, featuring Alex Kingston as River Song.

A full-length trailer for the new series was released yesterday.