By Mark SavageBBC Music Correspondent Image source, Getty ImagesImage caption, Oliver’s Army reached number two in 1979 Elvis Costello has revealed he will no longer perform his biggest hit, Oliver’s Army, and has also asked radio stations to stop playing the song. Written about the conflict in Northern Ireland, the lyrics contain a racial slur used to describe Irish Catholics. “That’s what my grandfather was called in the British army – it’s historically a fact,” he told The Telegraph. “But people hear that word… and accuse me of something that I didn’t intend.” Released in 1979, Oliver’s Army was played…