John Dempsey knows the London Tube Map like the back of his hand. The one he strums with, actually. In 1978, with Great Britain's Winter Of Discontent in full swing, Dempsey stepped into a life of excess the London guide books never tell you about. He'd seen a busker at London Bridge Underground, gathered up his courage, jumped the barrier to get into the station, threw his guitar case on the ground and did some quiet fingerpicking. A coin drops in. Then another. Next thing you know, he makes enough to buy milk for his tea. A guitar-strumming, hat-passing hippie star was born. A fictionalized