Davies was called to the bar at Lincoln's Inn in 1948, where he became a bencher in 1972 and was Treasurer in 1991. He practised on the Midland Circuit, and became a QC in 1964. He led the prosecution of Buster Edwards in 1966 for his part in the Great Train Robbery three years earlier, and of William Waite, the "gentle poisoner" who had killed his wife. He was the Leader of the Midland Circuit and a member of the Bar Council from 1968 to 1971, and then Joint Leader of the Midland and Oxford Circuit from 1971 to 1973.