In 1781, promoted to lieutenant-colonel of the newly formed and short-lived 102nd Regiment of Foot, he sailed to the East Indies, where he was given the local rank of colonel.

Promoted to major general in the 81st Regiment of Foot he was in 1795 appointed Governor of Saint Nicolas Mole, a French settlement in St Domingo (now Haiti) which had surrendered to the British forces.

Henry Dundas, 1st Viscount Melville, who was the Secretary of State for War to prime minister William Pitt the Younger, instructed Sir Adam Williamson, the lieutenant-governor of Jamaica, to sign an agreement with representatives of the French colonists that promised to restore the ancien regime, slavery and discrimination against mixed-race colonists, a move that drew criticism from abolitionists William Wilberforce and Thomas Clarkson.

[2][3] However, Toussaint L'Ouverture and his army of former enslaved people, under the command of Alexandre Petion, defeated the British forces.

[4] His eldest daughter Isabella married the writer Granville Penn in 1791 at All Saints Church, Kingston upon Thames.