Theodor Haak (1605-1690) came from the Palatinate, and arrived in England in 1620 after the defeat of Frederick V. He studied in both Oxford and Cambridge. Whilst in England he became involved with the administration of aid collections for the Palatinate churches, and worked closely with the stranger church of Austin Friars. He returned to Germany at various points, and also lived for a while in Amsterdam, where he oversaw the publication of Weckherlin’s anthology. He corresponded with learned men in Northern Europe, including the French mathematician Mersenne. Amongst Haak’s close acquaintances were two other men with German connections living in London: Samuel Hartlib, of dual English-German heritage, who was born in the Hanseatic city of Elbing, (today Elbląg in Poland), and John Dury, the son of a Scottish clergyman, also based in Elbing. Hartlib and Dury were part of an important European network of ideas in the middle of the century. Their efforts in the 1640s brought the Czech educational reformer Jan Amos Komenský, or Comenius, to England with his programme of Pansophism, Universal Knowledge. Unfortunately Comenius’s visit coincided with the chaos of the early years of the Civil War, scuppering his plans for the establishment of a universal college in England. But the legacy was to some degree realised during the Restoration, with the founding of the Royal Society. Several different streams fed into this, but one was a scientific group that met in London from 1645, which Robert Boyle termed ‘The Invisible College’. Haak was a member of this group, and when the Royal Society received its second charter in 1663 he was listed among the original members. In addition to his scientific interests, Haak worked as a translator, both for the English Parliament and independently, and he provided the majority of the first German translation of Milton’s Paradise Lost, although it was completed and published by Ernst Gottlieb von Berge in 1682. Haak shows the role played by London-based Germans in international networks, corresponding with important thinkers in Continental Europe and sharing scientific and intellectual developments.