ROLLING STONE Keith Richards had no idea who Johnny Depp was until the Hollywood superstar asked him to play his father in the new Pirates Of The Caribbean film The 63-year-old rocker admits he thought Depp was a "failed rock'n'roll artist" until he did his research and discovered the truth. Richards tells NME magazine, "He was just another of my son's friends. I didn't know what he did. "I thought he was a failed rock'n'roll artist, then I started to see his work. He called and said, 'Hey, Jesus Christ, I've copied you to do Pirates' - which I thought was the gentlemanly way of letting me know. "No wonder he paid for all the beers. I didn't realise I was being observed."