Thirty years ago, Bob Geldof staged Live Aid in London and Philadelphia to highlight the effects of famine in Ethiopia. He is one in a long line of famous faces who have campaigned for causes close to their hearts, with mixed success.
Idealism mixed with the PR and marketing savvy of show business made many stars realise they could use their image to raise awareness of social issues. But as some celebrities have discovered, knowledge is power when it comes to campaigning.