In September 1656 a London apothecary, Anthony Hinton, was arrested on suspicion of using his premises beside the Old Bailey as a clearing house for letters on their way to exiled Royalists on the Continent. Interrogated by Cromwell’s own intelligence officers, Hinton quickly confessed his guilt and gave up the names of a number of spies with ties to the Sealed Knot, one of the Royalist secret societies operating in England during the Commonwealth. His list included Susan Hyde, the sister of Sir Edward Hyde, one of Charles II’s closest advisers. Hinton claimed that she had been sending useful information to fellow Royalists for more than four years, using a variety of ciphers and codenames.

Hinton’s claims were true. Hyde’s last letter, written in September 1656, warned Charles II that there was a leak in the network. She suspected that a double agent was at work. So there was: Sir Robert Honywood, master of the household to Charles II’s aunt Elizabeth of Bohemia, was spying for Cromwell. But it was Hinton’s evidence that was Hyde’s undoing. Some weeks after his confession three officers arrived at the house in Wiltshire where she was staying. They ransacked her chamber, searched her for incriminating papers and carted her off to be examined in London, where she was so frightened by her interrogators that she had a mental breakdown. She died in prison at Lambeth a few days later and was soon forgotten. Even her brother, the great chronicler of the Civil Wars, made no mention in his writings of her contribution to the war effort. Broken and overlooked, she disappeared from history.

As Nadine Akkerman’s intriguing new book makes clear, in life, as in death, women spies – ‘she-intelligencers’ in the parlance of the day – passed unnoticed in the 17th century. If they were captured, they were usually released, partly in deference to their sex and partly because they were regarded