Catholic, Eastern Orthodox, Oriental Orthodox, Anglican, Old Catholic and some Lutheran bishops claim to be part of the continuous sequence of ordained bishops since the days of the apostles referred to as apostolic succession. Since Pope Leo XIII issued the bull "Apostolicae curae" in 1896, the Catholic Church has insisted that Anglican orders are invalid because of changes in the Anglican ordination rites of the 16th century and divergence in understanding of the theology of priesthood, episcopacy and Eucharist. However, since the 1930s, Utrecht Old Catholic bishops (recognised by the Holy See as validily ordained) have sometimes taken part in the ordination of Anglican bishops. According to the writer Timothy Dufort, by 1969, all Church of England bishops had acquired Old Catholic lines of apostolic succession recognised by the Holy See. This development has muddied the waters somewhat as it could be argued that the strain of apostolic succession has been re-introduced into Anglicanism, at least within the Church of England.