It is obvious that a "secret service" of this kind rendered the Jews a formidable hidden power, the more so since their very existence was frequently unknown to the rest of the population around them. This precaution was necessary because Jews were not supposed to exist at that date in England. In 1290 Edward I had expelled them all, and for three and a half centuries they had remained in exile; the Crypto-Jews or Marranos who had come over from Spain contrived, however, to remain in the country by skilfully taking the colour of their surroundings. Mr. Wolf goes on to observe that Jewish services were regularly held in the secret Synagogue, but "in public Carvajal and his friends followed the practice of the secret Jews in Spain and Portugal, passing as Roman Catholics and regularly attending mass in the Spanish Ambassador's chapel."[458] But when war between England and Spain rendered this expedient inadvisable, the Marranos threw off the disguise of Christianity and proclaimed themselves followers of the Jewish faith. Now, just at this period the Messianic era was generally believed by the Jews to be approaching, and it appears to have occurred to them that Cromwell might be fitted to the part. Consequently emissaries were despatched to search the archives of Cambridge in order to discover whether the Protector could possibly be of Jewish descent.[459] This quest proving fruitless, the Cabalist Rabbi of Amsterdam, Manasseh ben Israel,[460] addressed a petition to Cromwell for the readmission of the Jews to England, in which he adroitly insisted on the retribution that overtakes those who afflict the people of Israel and the rewards that await those who "cherish" them. These arguments were not without effect on Cromwell, who entertained the same superstition, and although he is said to have declined the Jews' offer to buy St. Paul's Cathedral and the Bodleian Library because he considered the £500,000 they offered inadequate,[461] he exerted every effort to obtain their readmission to the country. In this he encountered violent opposition, and it seems that Jews were not permitted to return in large numbers, or at any rate to enjoy full rights and privileges, until after the accession of Charles II, who in his turn had enlisted their financial aid.[462] Later, in 1688, the Jews of Amsterdam helped with their credit the expedition of William of Orange against James II; the former in return brought many Jews with him to England. So a Jewish writer is able to boast that "a Monarch reigned who was indebted to Hebrew gold for his royal diadem."[463]