Following her appearance as Donna in 'The Runaway Bride' last Christmas, Tate was asked to reprise the role just months later.
The comedienne revealed in the the new edition of Doctor Who Magazine: "When I was asked to do it, I genuinely couldn't believe they'd asked me. I was having lunch with [executive producer] Julie Gardner and it was the last thing I thought we were going to have a conversation about. She said it, and I nearly... well, I... even now, I just can't believe it. I'm speechless."
Tate also added that the experience of filming her initial one-off role played a huge part in her acceptance of the offer. "I love the show... and I love working with David [Tennant], so I just thought it was a fantastic opportunity. It was a bit of a no-brainer for me, really."