Churchill began playing the piano at the age of six and studied classical music until he was fifteen. He became interested in blues and rock music, and joined his first band Sons of Adam in Nottingham. Churchill then met Alvin Lee of The Jaybirds. At first, Churchill joined the band as its road manager, but he soon became the keyboard player. In November 1966 there was a name change to Ten Years After. With this group, Churchill played at major rock festivals including Woodstock in 1969, and the Isle of Wight Festival on 29 August 1970.
Ten Years After broke up in 1976 and Churchill became Professional Manager at Chrysalis Music; the company was then owned by his manager, Chris Wright. In 1977, he left to found Whitsett Churchill Music Publishing with Tim Whitsett, publishing and promoting American artists, especially from the south.