SEXBY, EDWARD (d. 1658), English soldier, “ leveller ” and conspirator, was a private soldier in Cromwell's regiment of horse when first heard of about 1643. He opposed the proposal to disband the army in 1647; and as one of the “ agitators ” he resisted all attempts to come to an arrangement with Charles I., and advocated extreme democratic doctrines. He rose to the rank of colonel, but was deprived of his commission in 1651. When Cromwell assumed the title of lord protector, Sexby became one of his most violent opponents, and in 1655 tried to bring together the levellers and the royalists in a combination to overturn the government. Compelled to fly from England, he intrigued with the Spanish government with a view to restoring Charles II., as the only feasible plan for destroying Cromwell; and he was concerned in several plots to assassinate the protector. About 1657 he wrote the celebrated apology for tyrannicide entitled “ Killing No Murder,” under the pseudonym William Allen, which was printed in Holland and distributed in England. In July 1657 he was arrested in disguise in England, whither he had come to attempt Cromwell's assassination, and he died in the Tower of London on the 13th of January 1658.