John Thurloe was born in Essex 1616 and was baptized June 12. His father was Thomas Thurloe, rector of Abbot's Roding.
Thurloe was trained as a lawyer in Lincoln's Inn. He joined the service of Oliver St. John. In January 1645 he became a secretary to the parliamentary commissioners at Uxbridge. In 1647 he was admitted to Lincoln's Inn as a member.
He remained in the sidelines during the English Civil War but after the accession of Oliver Cromwell, became part of his government. He supported the idea that Cromwell should adopt a royal title. In 1652 he became a secretary for state for the Commonwealth of England.
In 1653 he became the head of the intelligence and developed a widespread network of spies in England and in the continent. He hired mathematician John Wallis to establish a code-breaking department. Through this, he broke the Sealed Knot, secret society of Royalists and various other plots against the Protectorate.
In 1654 he also became a member of parliament and represented Ely. In 1655 he also became a head of post office, which allowed his service to intercept mail. In this capacity he exposed Edward Sexby's 1657 plot to assassinate Cromwell and captured would-be assassin Miles Sindercombe and his group.
In 1657 he became a member of Cromwell's second council and the governor of the Charterhouse. In 1958 he became a chancellor of Glasgow University.
After the death of Oliver Cromwell in 1658, he supported his son Richard Cromwell as the Lord Protector and became a part of his administration till the end of the Protectorate. In 1659 he represent Cambridge University in the parliament.
After the fall of Protectorate he lost his position in 1959 when various parties accused him of arbitrary decisions during his time as a head of intelligence. He was briefly reinstated as a secretary of state in February 27 1660 but resisted Restoration.
After the Restoration he was arrested for high treason in May 15 1660 but was not tried. He was released on June 29 on the condition that he would assist the new government upon request. He retired from public life but served as a behind-the-scenes authority of foreign affairs and wrote informative papers for Clarendon. However, he did not become part of any new administration.
John Thurloe died in February 21 1668 in his chambers in Lincoln's Inn and was buried in the chapel.
Thurloe's correspondence is kept in Bodleian Library, Oxford and in the British Museum. Thomas Birch published part of it in 1742. In his diary, Samuel Pepys spells his name as Thurlow.