Alex Kingston says she did not realise how popular Doctor Who was when she was offered the part of the Time Lord’s wife.

The 47-year-old, who first played the role in 2008, is returning to the sci-fi series as the Doctor’s other-half, River.

She told the February issue of Reader’s Digest: “I’m not allowed to breathe a word about the new storylines… otherwise, they take away my sonic screwdriver.

“When I was first offered the part, I had no idea how successful the new Doctor Who was because I was in the US. But as soon as I read the script, I fell in love with River.”

The former ER star, who lives in the States, said: “She provides a very complex link to the Doctor’s life and ever since I saw Alien, a little bit of me has wanted to run around a spaceship shooting intergalactic monsters.”

Alex also spoke about the issue of ageism and that it is more “ruthless” in the US than the UK. She said: “I had a bit of facial fat removed when I first started on ER, because they always had trouble lighting my face and it was making me a bit self-conscious.

“But it was definitely not about getting old! All that nipping and tucking? Sticking stuff in your lips? No, thank you!”

She continued: “Yes, ageism happens in the US, but ageism happens everywhere. Mind you, I have to admit that it’s not as ruthless in the UK.

“There always seem to be plenty of good female roles for actors in their thirties and forties. Look at some of the great soap characters. Maybe British audiences enjoy seeing more realistic TV.”

Alex can also been seen in the new ITV1 drama Marchlands which starts on Thursday, 3 February at 9pm. She spoke exclusively to about what’s in store for the new series.

Watch the video here.