guardian.co.uk, Tuesday 20 October 2009 13.45 BST Article history Thousands of Anglicans could defect to the Roman Catholic church after the pope today approved a new global institution to receive them. It will be the first time since the Reformation in the 16th century that entire Protestant communities have reunited with Rome. The first group likely to take advantage of the new rules is the Traditional Anglican Community (TAC), which broke off from the rest of the community in 1991 and claims to have more than 500,000 members worldwide. Other groups unhappy with developments in the Anglican Communion are also expected to accept the invitation from the Vatican. Traditionalists, including thousands in the Church of England, have long threatened to defect to Rome over issues such as the ordination of women and gay people. Reflecting the importance of the initiative, the pope set out the new arrangements in an apostolic constitution, the highest form of pontifical decree, and press conferences were held simultaneously in London and the Vatican to announce it. In Ecclestone Square, the administrative headquarters of the Catholic Church of England and Wales, the Anglican archbishop of Canterbury and the Catholic archbishop of Westminster sat side by side on the top table in a show of unity, but the choice of location reflected the shift in power. Both men played down any suggestion of tension brought on by the decision, but the unease became apparent in the question and answer session that followed. The archbishop of Canterbury, Rowan Williams, informed journalists that he only heard about the apostolic constitution "a couple of weeks ago" and that there was no input from or consultation with Lambeth Palace. His face reddened as he spoke and, at one point, the archbishop of Westminster, Vincent Nichols, answered questions relating to Williams's leadership and authority. Williams said: "I do not think this constitution will be seen as in any sense a commentary on Anglican problems offered by the Vatican. It is a response to this range of requests and inquiries from a very broad variety of people, either Anglican or of Anglican heritage. In that sense it has no negative impact on the relations of the communion as a whole to the Roman Catholic church as a whole. It is not an act of aggression, it is not a statement of no confidence. It is business as usual." Benedict's chief theological adviser, the US cardinal William Levada, who heads one of the most important Vatican departments, said the decree had been drawn up "to respond to the numerous requests that have been submitted to the Holy See by groups of Anglican clerics and believers from various parts of the world who wish to enter into full and visible communion" with Rome. He said that, under the new arrangements, Anglican communities that joined the Catholic church would be able to keep their own liturgy while remaining outside the existing dioceses. Their pastoral care would be entrusted instead to their own senior prelates, who would not necessarily become Catholic bishops. This is a way around the problem that in the Catholic church, as in the Orthodox churches, married men are not allowed to become bishops.