The Office of the Chief Rabbi is the institutional identity for the Chief Rabbi of the United Hebrew Congregations of the Commonwealth [UK]. Unlike in other European countries, individuals serving as the Chief Rabbi of the United Hebrew Congregations are not formally designated by an authoritative state or civic body. Rather, the "office" is occupied by the senior rabbi of the United Synagogue, the umbrella institution for its affiliated Orthodox and Ashkenazi synagogues in the United Kingdom. The position of Chief Rabbi in the UK grew out of an 18th century desire among British Jewry for a respected representative figure comparable to the Archbishop of Canterbury for Anglican Christians. Rabbi Aaron Hart (1670–1756), rabbi of the Great Synagogue in London since 1704, was thus regarded by the 1750s as the first of the British chief rabbis. Over the next century and as British Jewry continued to grow, by the tenure of Rabbi Nathan Marcus Adler (from 1845-1890) the communal leadership and halakhic authority of the position had become firmly established. When in 1870, the Great Synagogue joined with four other synagogues, and was formally recognized as the United Synagogue by an Act of Parliament, the Chief Rabbi was legally established as its head. The current chief rabbi of the UHC and senior rabbi of the United Synagogue is Rabbi Sir Ephraim Mirvis. (The Office of the Chief Rabbi should not be mistaken for the London Beit Din, the Court of the Chief Rabbi of the United Hebrew Congregations.)