other hand, was not nominally Christianised until 995 AD when Olaf Tryggvason ordered that if the earl and his subjects did not convert, he would be killed and the islands ravaged. The Roman Catholic Church remained the dominant form of Western Christianity in Britain throughout the Middle Ages, but the (Anglican) Church of England became the independent established church in England and Wales in 1534 as a result of the English Reformation. It retains a representation in the UK Parliament and the British monarch is its supreme governor. In Scotland, the Presbyterian Church of Scotland, established in a separate Scottish Reformation in the sixteenth century, is recognized as the national church. It is not subject to state control and the British monarch is an ordinary member, required to swear an oath to "maintain and preserve the Protestant Religion and Presbyterian Church Government" upon his or her accession. The adherence to the Catholic Church continued at various levels in different parts of Britain, especially among recusants and in the north of England, but most strongly in Ireland. This would expand in Great Britain, partly due to Irish immigration in the nineteenth century, the Catholic emancipation and the Restoration of the English hierarchy. Particularly from the mid-seventeenth century, forms of Protestant nonconformity, including Congregationalists, Baptists, Quakers and, later, Methodists, grew outside of the established church. The (Anglican) Church in Wales was disestablished in 1920 and, as the (Anglican) Church of Ireland was disestablished in 1870 before the partition of Ireland, there is no established church in Northern Ireland. The Jews in England were expelled in 1290 and only emancipated in the 19th century. British Jews had numbered fewer than 10,000 in 1800 but around 120,000 after 1881 when Russian Jews settled permanently in Britain. The substantial immigration to the United Kingdom after World War II has contributed to the growth of foreign faiths, especially of Islam, Hinduism and Sikhism. Buddhism in the United Kingdom experienced growth partly due to immigration and partly due to conversion (especially when including Secular Buddhism). As elsewhere in the Western world, religious demographics have become part of the discourse on multiculturalism, with Britain variously described as a post-Christian society, as "multi-faith", or as secularised. Scholars have suggested multiple possible reasons for the decline, but have not agreed on their relative importance. Martin Wellings lays out the "classical model" of secularisation, while noting that it has been challenged