He lectured at a wide array of universities, including Cairo (1965-66 as visiting professor), Tübingen, Bonn and All Souls College, Oxford (as visiting fellow).
His later substantial books include The Origins of Osiris and his Cult (1980), Atlantis and Egypt (1991), The Divine Verdict (1991), and Triads and Trinity (1996) as well as contributing to The Cambridge History of Judaism (1999).