The English Church continuously adhered to the See of Rome for almost a thousand years from the time of Augustine of Canterbury; but in 1534, during the reign of King Henry VIII, the church, through a series of legislative acts between 1533 and 1536, became independent from the Pope for a period as a national church with Henry declaring himself Supreme Head. Under Henry's son, King Edward VI, the Church of England became more influenced by the European Reform movement.
The English Church was brought back under full papal authority in 1553, at the beginning of the reign of Queen Mary I, and Catholicism was enforced by the Marian persecutions; however, when Queen Elizabeth I came to the throne in 1558, the Church of England's independence from Rome was reasserted through the settlement of 1559, which shifted the Church of England's teaching and practice, and in the Act of Uniformity, which caused a rift between Catholics and Queen. In 1570 Pope Pius V responded, in his bull Regnans in Excelsis, calling on all Catholics to rebel against Elizabeth and excommunicating anyone who obeyed her. The Parliament of England made the fact of being a Jesuit or seminarian treasonable in 1571. Priests found celebrating Mass were often hanged, drawn and quartered, rather than being burned at the stake. The Catholic Church (along with other non-established churches) continued in England, although it was at times subject to various forms of persecution. Most recusant members (except those in diaspora on the Continent, in heavily Catholic areas in the north, or part of the aristocracy) practised their faith in private for all practical purposes. In 1766, the Pope recognised the English Monarchy as lawful, and this led eventually to the Roman Catholic Relief Act 1829. Dioceses (replacing districts) were re-established by Pope Pius IX in 1850. Along with the 22 Latin Rite dioceses, there are the Eastern Catholic diocese of the Ukrainian Catholic Eparchy of Holy Family of London and the Syro-Malabar Catholic Eparchy of Great Britain.
At the 2001 United Kingdom census, there were 4.2 million Catholics in England and Wales, some eight per cent of the population. One hundred years earlier, in 1901, they represented only 4.8 per cent of the population. In 1981, 8.7 per cent of the population of England and Wales were Catholic. In 2009, an Ipsos Mori poll found that 9.6 per cent, or 5.2 million persons of all ethnicities were Catholic in England and Wales. Sizeable populations include North West England where one in five is Catholic, a result of large-scale Irish immigration in the nineteenth century as well as the high number of English recusants in Lancashire.
Much of Great Britain was incorporated into the Roman Empire in 43 AD, after Claudius led the Roman conquest of Britain, conquering lands inhabited by Celtic Britons. The indigenous religious traditions of the Britons, under their priests the Druids were suppressed; most notably Gaius Suetonius Paulinus launched an attack on Ynys Môn in 60 AD and destroyed the shrine and sacred groves there. In the years following this, Roman influence saw the importation of several religious cults into Britain, including Roman mythology, Mithraism and the imperial cult. One of these sects, then disapproved by the Roman authorities, was the Levantine-originated religion of Christianity. While it is unclear exactly how it arrived, the earliest British figures considered saints by the Christians are St. Alban, followed by Ss. Julius and Aaron, living in the 3rd century.
Eventually, the position of the Roman authorities on Christianity moved from hostility, to toleration with the Edict of Milan in 313 AD and then enforcement as state religion following the Edict of Thessalonica in 380 AD, becoming a key component of Romano-British culture and society. Records note that Romano-British bishops, such as Restitutus, attended the Council of Arles in 314, which confirmed the theological findings of an earlier convocation held in Rome (the Council of Rome) in 313. The Roman departure from Britain in the following century and the subsequent Germanic invasions sharply decreased contact between Britain and Continental Europe. Christianity, however, continued to flourish in the Brittonic areas of Great Britain. During this period certain practices and traditions took hold in Britain and in Ireland that are collectively known as Celtic Christianity. Distinct features of Celtic Christianity include a unique monastic tonsure and calculations for the date of Easter. Regardless of these differences, historians do not consider this Celtic or British Christianity a distinct church separate from general Western European Christianity.