 In 1974 he left the UK to become professor of religious studies and history at the University of California, Santa Cruz, where, for three years he chaired the religious studies department.He returned to England with his wife in 1980, but was appointed rector of the Tantur Ecumenical Institute for Theological Studies at Jerusalem from 1981 to 1985.He retired to Betley, near Keele in Staffordshire, becoming senior research fellow at the Multi-Faith Centre, Selly Oak Colleges, Birmingham, and continuing to write.