In 1928, after an illustrious career as undergraduate at Oxford University, Butler, baptized in the Church of England, was received into full communion with the Roman Catholic Church. In 1929 he became a monk of the Benedictine community of Downside Abbey – a House of the English Benedictine Congregation – and was ordained priest there in 1933. In 1946 the community elected him as their Abbot, which he remained for twenty years until his consecration in 1966 as Titular Bishop of Nova Barbara and Auxiliary Bishop to Cardinal John Carmel Heenan in the Archdiocese of Westminster.