(The illustration shows Old Jewry on the Agas Map, a woodcut made of London probably in the 1560s. It shows Old Jewry [in yellow] linking Poultry Street to Gresham Street. The street is still called Old Jewry, as you can see in the illustration to this 2012 post.)
Although Jews could travel anywhere and any time, they likely came to England in larger numbers from Rouen after 1066, when William invited them to take up residence. By that time Jews were well-known as money-lenders, and William knew he would need money to finance his consolidation of his new country.
Because of their financial importance to the Crown, London Jews were given rights by some kings. William's son William Rufus brought rabbis and priests together in London t debate religion, teasing his priests that if the Jews won then Rufus would convert.
After the suspicious death of Rufus, Henry I continued the royal policy of giving the Jews privileges unavailable to regular subjects. Jews were a valuable source of financial support; the king would occasionally tax them to raise money quickly. Henry issued a royal charter giving Jews certain protections and freedoms. Jews were given freedom of movement without having to pay the king's tolls, the right to be tried by their Jewish peers, and the right to swear on the Torah in a court of law.
Besides the mikveh, Jewry street also contained the Great Synagogue, which was closed in 1272 after the death of Henry III—who "supported" the Jews with his charity institution, the Domus Conversorum ("House of Converts") placed on the western edge of London far from Jewry, possibly to help prevent apostasy—and the rise to power of Edward I.
One of the other chief locations of Jews in England after they came from the continent in the 11th century was Oxford, and we'll look at their presence there tomorrow.