Discussing the mystery’s explanation, Coleman told TV Guide: “I only found out whilst reading the last episode of our season, which was a couple of months before we finished shooting. So I played most of the season not knowing, which is really good. I didn’t need to know in order to play what I needed to do. It’s being slowly teased throughout the series. It’s like this slowly unfolding mystery, and we will eventually get payoff.”

The actress also revealed that viewers will discover why the birthday of the Clara seen at Christmas is 23 November – the same date that Doctor Who first aired in 1963: “In the Christmas episode, I didn’t know why that was the case. But again, we will find out by the end of this series. But it’s really exciting — [the series finale] is phenomenal. My spine was tingling when I read it. Again, I’m teasing your so badly here, but there’s the beginning opening sequence, which [is] kind of building up into the 50th. It’s just huge.”

She has also hinted that Clara and the TARDIS will have “a bit of a face-off”.

Series 7’s finale will air on BBC One on Saturday 18 May 2013. The official mini-synopsis teases: “Someone is kidnapping the Doctor’s friends, leading him towards the one place in all of time and space that he should never go…”

Coleman is current filming the show’s 50th anniversary special.

> Catch up on all the 50th Anniversary Special news and rumours so far in our summary.

What are your threories on the mystery of Clara? Let us know below…

> Order Series 7 Part 2 on DVD on Amazon.

> Buy Series 7 Part 1 on DVD on Amazon.

Watch the Series 7 Part 2 trailer…