http://cf.uba.uva.nl/en/collections/rosenthaliana/menasseh/19f5/index.html
In 1644, Menasseh met Antonio de Montezinos, a Portuguese traveler and Marrano Sephardic Jew who had been in the New World. Montezinos convinced him of his conclusion that the South America Andes' Indians were the descendants of the lost ten tribes of Israel. This purported discovery gave a new impulse to Menasseh's Messianic hopes, as the settlement of Jews throughout the world was supposed to be a sign that the Messiah would come. Filled with this idea, he turned his attention to England, whence the Jews had been expelled since 1290. He worked to get them permission to settle there again and thus hasten the Messiah's coming.
also https://www.chabad.org/library/article_cdo/aid/111879/jewish/Menasseh-Be...
from .. https://en.wikipedia.org/wiki/Menasseh_Ben_Israel
Oliver Cromwell was sympathetic to the Jewish cause, partly because of his tolerant leanings but chiefly because he foresaw the importance for English commerce of the participation of the Jewish merchant princes, some of whom had already made their way to London. At this juncture, the English gave Jews full rights in the colony of Surinam, which they had controlled since 1650. There is some debate among historians, particularly Jewish historian Ismar Schorsch, concerning whether or not Menasseh’s personal motives for pursuing the readmission of the Jews by England were primarily political or religious. Schorsch argues that the idea of England being a final place for Jews to inhabit in order to bring about the coming of the Messiah was hardly present in Hope of Israel, but rather was developed by Menasseh later in order to appeal to English Christians with Millenarianbeliefs.[9]
In 1655, Menasseh arrived in London. During his absence from the Netherlands, the Amsterdam rabbis excommunicated his student, Baruch Spinoza. In London, Menasseh published his Humble Addresses to the Lord Protector, but its effect was weakened by William Prynne's publication of Short Demurrer. Cromwell summoned the Whitehall Conference in December of the same year.
from... https://www.haaretz.com/jewish/.premium-1657-man-who-moved-cromwell-to-l...
Despite his many vocations, Menasseh had a hard time supporting his wife, the former Rachel Abarbanel, and their three children, so in 1638, he resolved to seek his fortune in the Dutch colony in Brazil. It is not known if he ever actually traveled to the New World but, in the meantime, the brothers Abraham and Isaac Pereira offered him the leadership of a new yeshiva, which enabled Menasseh to remain in Amsterdam. There, one of his students was Baruch de Spinoza.
Mystical quest – to England
Menasseh ben Israel was also a student of kabbala and, as such, subscribed to the Jewish mystical belief that the Messiah’s coming would be precipitated by the spreading of the Children of Israel to the far corners of the world. An encounter with the converso Portuguese Jewish traveler Antonio de Montezinos, who had been to the New World, convinced him that the native Americans who Montezinos met there were descendants of the Lost Tribes of Israel.
In contemporary geographical terms, this left England – referred to in medieval Hebrew as “Ktzeh Ha’olam” (“end of the earth,” a term that appears in Deuteronomy 28) – from which Jews had been expelled in 1290, as the place Jews needed to reenter if the messianic age was to arrive.
Thus, in 1651, Menasseh sent his son, Samuel, and brother-in-law, David Abravanel Dormido, to England to seek to negotiate with the Lord Protector, Oliver Cromwell, on the question of readmission. Failing at that mission, Samuel urged Menasseh himself to come to London. Menasseh did so that year, and was therefore absent when Spinoza was banished from the Jewish community of Amsterdam in July 1656.
At the urging of Menasseh, who dedicated the Latin edition of his book “Mikveh Israel” to the English Parliament, Cromwell convened the Whitehall Conference in December 1655 to discuss the question of the Jews’ readmission.
Although the conference was unable to come to definitive agreement on the subject, and Cromwell chose not to push its participants on it, there was consensus that “there is no law against their [the Jews] coming,” which served as the wedge for just that to happen, and for permission being given to Jews to establish both a synagogue and a cemetery in London.
Menasseh barely lived to enjoy the privilege. He was in the Netherlands when he died, on this day in 1657, having accompanied the body of Samuel, his son, home for burial. Menasseh is buried in the Beth Haim cemetery in Oudekerk aan Amstel, outside Amsterdam.