Once in England, Starkey's reputation as an alchemist and chymical furnace maker grew among the scientific community and he soon acquired a network of colleagues from the circle of friends and correspondents of Samuel Hartlib – a group of social reformers, utopians, and natural philosophers. Within a few years, however, Starkey found himself in financial trouble and was consequently incarcerated because of debt—possibly twice sometime in late 1653 and again in mid-1654. Imprisoned for a brief period of time, Starkey returned to the practice of alchemy and medicine upon his release in late 1654. Additionally, he wrote and published a number of popular treatises. Yet, his most important work was written under several pseudonyms during the period prior to imprisonment when he was associated with the Hartlib circle. The most famous of these works, the "Introitus apertus ad occlusum regis palatium", was published in 1667 after his death.