Spying on the post

The mail has been such an important communications tool that it has frequently been used to deliver matters of national importance, and to uncover secret plots. Oliver Cromwell’s Principal Secretary of State John Thurloe relied on regular interception of the mail for intelligence purposes. Thurloe’s spies exposed Edward Sexby's 1657 plot to assassinate Cromwell. Had he not done so, the landscape of the United Kingdom might have been considerably different today. Cromwell’s son Henry wrote to Thurloe: ‘Really it is a wonder you can pick so many locks leading into the hearts of wicked men as you do.’