Line of Duty star Kelly Macdonald has revealed the creator of the BBC show thought her Scottish accent would 'mess with Martin Compston's head'.
Series 6 has already had fans on the edge of their seat, with the Trainspotting actress joining the cast as a guest lead playing the mysterious Detective Chief Inspector Joanne Davidson.
The Glasgow-born actress says Line of Duty creator Jed Mercurio was 'delighted' with her Scottish accent during the script read-through, as he joked it might make Martin slip up.
The actor, who is from Greenock, plays DS Steve Arnott in the show, but has ditched his real voice in favour of an English accent.
Kelly told Radio Times.: "Oh my God! And my accent was a big joke for Jed Mercurio.
"He was delighted in the readthrough because he thought my accent would mess with Martin’s head and make it harder for him to maintain his English accent.
"Not that I do that many scenes with Martin."
Speaking about his English accent in the past, Martin told Radio X host Gordon Smart and Matt Morgan that fans got really 'riled up' about it.
"I can't play everything as if I'm from Greenock! I'm an actor!” he explained.
"You can't just go into every job saying: 'I'm doing my own accent'."
"The brief came in as a London detective.
"I came in doing a London accent, which I'm sure another 20 or 30 actors did, and I got the part,” he went on to explain.
"So it's never been a thing, but for some reason people get riled up about it."
When Kelly was offered the part in Line Of Duty she considered turning it down, as the nerves and pressure to do the popular show justice kicked in.
She bumped into Martin at an awards show who told her: "You've got to do it!"
Previous guest stars on the show have included Thandie Newton and Keeley Hawes.
The latter starred in the second and third series of the programme as Lindsay Denton.
Kelly said the actress was a “big act to follow” but ultimately convinced her to take the role.
She admitted that learning the lines was one of the hardest parts of the job.
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