Academically able, he won a Brackenbury scholarship to Balliol College, Oxford, where he studied political philosophy under A. D. Lindsay and was tutored in medieval history by Maurice Powicke.
He returned to England with his wife in 1980, but was appointed rector of the Tantur Ecumenical Institute for Theological Studies in 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.
In addition to his academic pursuits, Nicholl taught church history to the Poor Clares in Aptos, California, and to novices in the Missionaries of Charity, Mother Teresa's order, in London.
More informally he conducted a class in the "Penny University" at the Caffe Pergolesi in Santa Cruz, reading through Dostoevsky's The Brothers Karamazov.