We earn a commission for products purchased through some links in this article. Who is Philip Osborne in Line of Duty? Document No42 in your case files. episode 6. While it seems like only yesterday we first met DI Jo Davidson, things are about to come to an end in shocking style. The current run of episodes has brought back everyone including Patricia Carmichael, Steph Corbett, Patrick Fairbank, Jimmy Lakewell, and even Jesus, Mary, Joseph and the wee donkey. Other obscure alumni have included Lindsay Denton's kettle prison guard. However, it's the big name of Chief Constable Philip Osborne that's got everyone talking.