By Seamus Duff An EastEnders icon turned Ted Lasso star is joining the cast of Casualty for special scenes celebrating Derek Thompson’s exit as Charlie Fairhead. The BBC’s long-running medical drama has been on the air since 1986 – with 75-year-old Derek playing Charlie since the very first episode. This year, however, the actor will bow out after 38 years of service – and the show writers have big plans to make the exit of his character. To boost scenes, 73-year-old actress Annette Badland will be joining the cast in order to play Charge Nurse Shirley in flashback scenes set in the 1980s. Ann…