Line Of Duty star Kelly Macdonald has admitted she struggled to get her head around the show's legendary range of acronyms. The actress (45), who plays DCI Joanne Davidson in the latest series of the award-winning police drama, sought the help of her co-stars to learn some of the abbreviations including OCG, CHIS and ARU after being baffled with writer Jed Mercurio's script. In an interview with The Mirror, Macdonald admitted the acronyms made her so nervous, she didn’t immediately accept her role in the show. She said: "I did have to think about it. The shock, really, was when I read the first episode. Suddenly it was just, ‘Oh, there’s a massive long stream of dialogue about stuff I’ve never heard of'.