The United Synagogue (US) is a union of British Orthodox Jewish synagogues, representing the central Orthodox movement in Judaism. With 62 congregations (including 7 affiliates and 1 associate, ), comprising 40,000 members, it is the largest synagogue body in Europe. The spiritual leader of the union is the Chief Rabbi of the United Hebrew Congregations of the Commonwealth – a title that bears some formal recognition by the Crown, even though his rabbinical authority is recognised by only slightly more than half of British Jews. History The United Synagogue was mandated by an Act of Parliament in 1870, granting formal recognition to a union of three London synagogues forged by Nathan Marcus Adler, who bore the title of Chief Rabbi of the British Empire. Leaders of the organization included Nathan Rothschild, 1st Baron Rothschild, who served as president in 1910. At the time of its inception, the United Synagogue was the dominant force in Jewish communal and religious organization, though the organization lost some of its hegemony in the 1880s with mass migrations of Jews from Eastern Europe, who brought with them strains of Hassidic Judaism, Reform Judaism and secularism. In 1887, Jewish community leader Samuel Montagu created the Federation of Synagogues, which worked to unite Orthodox synagogues of Russian and other eastern European migrants living in the slums of East London. Today, the Federation serves 21 synagogues, compared to the United Synagogue's 64. There are also numerous orthodox synagogues in Britain, including Haredi, Chabad, and others, unaffiliated with United Synagogue. In addition, there are congregations of Reform, Masorti and Liberal Jews that are not included in the United Synagogue; so that, today, the organisation represents about 30 percent of all British congregants. Since 1990, central Orthodoxy has declined from 66 percent to 55 percent of total congregants, though this decline has flattened out in recent years. In 1970, the United Synagogue celebrated its centenary. Events included a special service held at the St. Johns Wood Synagogue, an exhibition of Jewish artefacts held at the Christies Auction Rooms, and a celebratory banquet held at the Dorchester Hotel in the presence of the Queen and the Duke of Edinburgh. This was the first time that the Queen had attended an event held by the Anglo Jewish community, although the Duke of Edinburgh had previously attended the tercentenary commemoration of the return of Jews to England during the period of Oliver Cromwell.