[3] In 1652 a reward of £300 was by the English Commonwealth government set upon his head, yet at the conclusion of the war he was permitted to enter the Spanish service with 1,200 of his men.

When James II came to Ireland following the Glorious Revolution, Grace was appointed Governor of Athlone, with a garrison of three regiments of foot, and eleven troops of cavalry.

When called upon to surrender, he fired a pistol over the messenger's head, and declared: "These are my terms; these only will I give or receive; and when my provisions are consumed, I will defend till I eat my old boots."

Nevertheless, he made a heroic defence under St Ruth, and on 30 June 1691, after de Ginkell's passage of the Shannon and the capture of the citadel on the Connaught side, Colonel Grace's body was found under the ruins.

His conduct towards the Protestants within his district is described as having been peculiarly humane and just; and although the severity of his discipline contrasted with the irregularities tolerated in other portions of the Irish army, he was greatly beloved by his men.