Keeley Hawes has admitted she is feeling the pressure about her forthcoming Doctor Who appearance.
But the Line Of Duty star told The Independent working with Peter Capaldi on the sci fi show had put her at ease, as they are old friends.
Keeley is appearing as villainous banker Ms Delphox in the new series, which returns to BBC One in August with Peter installed as the new Time Lord.
The former Spooks actress confessed: "It was quite nerve-wracking going on such a big show.
"It feels like a big show because it is so well known and people love it so much, there's a big old Who fanbase out there, so you've got all that pressure. I hope people enjoy my episode - it's really good fun."
Keeley said of working with Peter: "We were in a terrible thing together years ago but a really, good fun thing.
"So, I knew him and Douglas McKinnon who directed the first three episodes of Line of Duty was directing it, so I felt very relaxed about that.
"But he's just brilliant. Peter Capaldi is just fabulous - I think everyone's going to love him."
The Doctor and his companion Clara are set to meet Ms Delphox during a visit to a mysterious planet. The episode has been penned by Sherlock writer Steve Thompson, who also wrote the Doctor Who adventures The Curse of the Black Spot and last year's Journey to the Centre of the TARDIS.