The Welsh bishops refused to co-operate with Augustine of Canterbury's mission to the Anglo-Saxons. However, a combination of Celtic Christianity's reconciliation with Rome and English conquest of Wales meant that from the Middle Ages until 1920, the Welsh dioceses were part of the established Church of England in its Province of Canterbury. They were all in communion with Rome until the Reformation made them independent of Rome and under the control of King Henry VIII. The Established Church in Wales was the Church of England until it was disestablished in Wales in 1920. The old Welsh dioceses became the new Church in Wales. It created a new diocese in 1921, the Diocese of Monmouth.