In Britain today, most Jews affiliate with one of six umbrella organisations. These include The Reform Synagogues of Great Britain, Liberal Judaism, The Assembly of Masorti Synagogues in Great Britain, The Federation of Synagogues, and The Union of Orthodox Hebrew Congregations. By far the largest is The United Synagogue, the umbrella organisation for Modern Orthodox Judaism in Britain. If you visit a United Synagogue on a Saturday morning, you will be able to identify the Rabbi very easily, he will be the one wearing the black robes and the big hat. Where do these robes come from?
In the early 1800’s the Reform Movement began in Germany and began to attempt to Christianize itself in order to assimilate with the general population. To this end, they began running services in German, and encouraging their rabbis to dress like Christian monks, specifically Greek Orthodox ones. Greek Orthodox monks wear long flowing black robes with circular black hats which protrude from the top of the head.
In Britain, it was long felt that Jewish Rabbis did not have a defining identifying symbol, in the way that Christian priests have a dog collar (or Roman Collar to give it its proper name). So, for a time, Rabbis were made to wear dog collars by the United Synagogue. In 1967, Immanuel Jacobovits was made Chief Rabbi of the United Synagogue, and decided to change this practice, making Rabbis wear long coats. More recently, Rabbis have been given an identifying symbol which has a Jewish background: The robes of the Rabbis of the German Reform Temples.
It is interesting to note that it is a sack-able offence for a Rabbi to not wear these robes on a Shabbat service!