My guest today is Tracy Daugherty who joins me to discuss his book 'We Shook Up Th World - The Spiritual Rebellion of Muhammad Ali and George Harrison'.

Ali met George in a Florida boxing ring in February 1964 - and ten years later as Ali was staging one of the great sporting comebacks George was struggling across America on his Dark Horse tour - Tracy's book looks at the journey these two men took over those 10 years and how 60's icons dealt with the changing world of the 70's.