He completed his doctoral thesis in 1975, "The Hiddenness of Wisdom in the Old Testament and later Judaism" at Regent's Park College (the Baptist permanent private hall at Oxford) while undergoing ministerial formation.
Fiddes was ordained as a minister in the Baptist Union of Great Britain in 1972, and has extensive ecumenical concerns, including being a Canon Emeritus of Christ Church Cathedral, Oxford and Prebendary of St Endellion in North Cornwall.
He was appointed Principal of Regent's Park in 1989 and was awarded the Title of Distinction of Professor of Systematic Theology in the University of Oxford in 2002.
[citation needed] In 2004 Fiddes was elected an Honorary Fellow of St Peter's, on which occasion he was described as being "recognised internationally as one of the leading scholars in the fields of theology and literature".
In 2002 he was chosen to preach the university Sermon on the Grace of Humility, and in 2005 he was appointed to deliver the Oxford Bampton Lectures, choosing as his topic Seeing the world and knowing God: ancient wisdom and modern doctrine.
[26] He shares the latter honour with Rowan Williams, whom he "vested in the traditional fur almuce" upon the occasion of his admission and installation as a prebendary.
[27] In 2009, Fides delivered the Holley-Hull Lectures at Samford University on the subject Telling the Christian Story in Our World Today.
[23][31] Fiddes was a keynote speaker at "The Power of the Word: Poetry, Theology and Life", a conference held jointly between Heythrop College and the Institute of English Studies.
[32] Fiddes was also a keynote speaker at the 2010 Biennial Conference of the International Society for Religion, Literature and Culture, St Catherine's College, Oxford (23–26 September 2010) on the topic "Attending to the Other: Critical Theory and Spiritual Practice".
[33] Past Event and Present Salvation: the Christian Idea of Atonement (London: Darton, Longman, & Todd, 1989), one of Fiddes's most important works, was studied by the Reverend Father Eamonn Mulcahy, C.S.Sp., in his doctoral thesis at the Pontifical Gregorian University under the supervision of the distinguished Australian Jesuit scholar Gerald O'Collins.
His thesis, which was entitled The Cause of Our Salvation: Soteriological Causality According to Some Modern British Theologians, 1988-98, also considered works by Colin Gunton, Vernon White, and John McIntyre.
It was reviewed in the online newspaper The Baptist Times by Hugh Whittaker, who wrote "A Unicorn Dies operates on several levels.