Distinguished Professor of Philosophy Brian Davies has published Thomas Aquinas's Summa Theologiae: A Guide and Commentary (OUP, 2014). It is now the longest and most comprehensive commentary to the Summa available in English. The publisher writes:
Following a scholarly account of Thomas Aquinas's life, Davies explores his purposes in writing the Summa Theologiae and works systematically through each of its three Parts. He also relates their contents and Aquinas's teachings to those of other works and other thinkers both theological and philosophical. The concluding chapter considers the impact Aquinas's best-known work has exerted since its first appearance, and why it is still studied today. Intended for students and general readers interested in medieval philosophy and theology, Davies's study is a solid and reflective introduction both to the Summa Theologiae and to Aquinas in general.
Professor Davies is now working on a commentary to the Summa Contra Gentiles. Updates to follow.