 A prominent representative of the Anglo-Catholic school of theology, he seems however to have avoided the narrowness of outlook of some more conservative Christians and played an important role in Jewish-Christian dialogue in the Cardiff area.There is some suggestion that Thomas was considered as a candidate for episcopal appointments during the 1950s, but was not in the event chosen to head a diocese until 1968 when he was elected and consecrated as Bishop of Monmouth.He was translated to Llandaff in 1970.