 In 1715 Blair joined the rebellion led by the Earl of Mar and travelled with the Jacobite army when it marched into England.He was captured at the Battle of Preston in November 1715 and imprisoned at Newgate Prison in London.Despite claiming that he had been forced to join the rebel army, he was sentenced to death, but was given a last-minute reprieve in April 1716 after appeals by Hans Sloane and other members of the Royal Society.