Keeley Hawes convinced Kelly Macdonald to sign up for 'Line of Duty'.
Kelly, 45, has joined the BBC's police corruption drama as DCI Joanne Davidson for the upcoming sixth season and she was nervous about taking on the role, but Keeley - who previously played DI Lindsay Denton - gave her some encouragement.
Speaking to Radio Times magazine, Kelly said: "The real issue was the sheer number of words I had to learn.
“When I saw the script, my first instinct was to run a mile. It’s all addresses and dates and police jargon, especially when I was interviewing suspects.
"Keeley was brilliant; she talked me down from the ledge. She said it might look as though you are being asked to do something completely impossible, but it’s not.”
The 'Trainspotting' star hadn't even watched the show before being cast, and once she did tune in she was too intimidated to watch Thandie Newton's acclaimed performances as DCI Roseanne 'Roz' Huntley.
Kelly added: "I’ve not watched lots of things! I saw bits of it on 'Gogglebox' and of course I was aware of its success…
"I got halfway through season four and stopped because it was getting too close to the start of the shoot.
"I was getting proper nerves and watching Thandie Newton wasn't making it easier!"
Kelly even considered turning down the role, but co-star Martin Compston reassured her.
She explained: "He was so excited. He said, ‘Hey! You’ve got to do it!’ It got to the point where I didn’t feel I could run away from it.
"I thought it might actually be a good challenge and it really was. Although I still can’t believe I got through some of it.”
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