Pete Doherty and Sir Paul McCartney got on "like father and son" when they met for a heart to heart.The troubled Babyshambles singer - who has spent the last month fighting his drug addiction at Wiltshire's Clouds rehab centre - promised the Beatles legend he is serious about cleaning up his act. A friend of Pete's told Britain's Daily Mirror newspaper: "He was overwhelmed by meeting Paul. They had a real heart to heart - at times it was like a father talking to his son. Pete promised Paul he was serious about getting clean, was through with the drugs, and said he never wanted to fall back into his dark days again."Pete, who was allowed to leave rehab to interview Paul for the Observer Music Monthly magazine the other day, received some much needed advice from the musician.The source added: "They spoke about everything from music, other singers and even touched on the subject of women - but that was strictly between the two of them."Pete didn't sleep the night before just thinking about what he would say to the legend when they actually came face to face. But they got on really well, and Pete found Paul very supportive."