In 1775, Thistlewood apprenticed Mulatto John to William Hornby as a carpenter. John was unhappy with his apprenticeship, and looked forward to the time when he could serve in the militia and get away from Hornby. One day in 1779, when John refused to go to work, Thomas had him flogged "pretty well" to persuade him to change his mind. When war broke out with the American colonies, John joined the "Brown Infantry", a regiment for mixed-race Jamaicans, to prepare for a French invasion that never came.