The actress played Federal Bureau of Investigation (FBI) agent Dana Scully opposite David Duchovny in the hit sci-fi show for nine years before it ended in 2002, and she revisited the role for a 2008 big screen movie.

Last year (15) it was announced the popular show would be returning for a six-episode run in 2016, but Gillian, 47, has now revealed how the passage of time left her struggling to complete any physically demanding scenes.

She tells The Observer Magazine, "I was ambivalent about the idea at first. In its old incarnation, we used to do 24 shows a year. But I can't do that any more, so it only became a reality once the networks started to be a bit more lenient about the number of episodes they were willing to air.

"What was weird once we started was that it was both strange and familiar. We're both a lot older now. I used to be able to run forever, but now I'm, like: my legs aren't working. The physical side was... challenging."