Complex sentence: He returned to Cambridge in 1967 as an assistant director of research at the Cavendish Laboratory, becoming a reader in physics in 1972 and a full professor in 1974, a position he held until he retired in 2007.
Split into simpler sentences: He returned to Cambridge in 1967 as an assistant director of research at the Cavendish Laboratory. He became a reader in physics in 1972 and a full professor in 1974, a position he held until he retired in 2007.