At the end of the civil war, Cromwell promoted Blood to the rank of Captain. Three years later he was elevated to Commissioner of Parliament. Blood is most famous for devising a plot to steal the Crown Jewels from the Tower of London and using them as a ransom for Charles II. In 1671 he and Maria disguised themselves as a parson and his wife. They visited the keeper of the jewels and Maria pretended to faint to cause a distraction.