O’Callaghan, whose elder brother Cornelius had been created Baron Lismore in the Irish peerage in 1785, was a soldier who had fought at Bunker Hill and later served in the West Indies.
He married for a second time at the age of 83, and died in February 1836. One local newspaper accorded him this flowery tribute:
He has for many years resided at Heighington, surrounded by a social and highly respectable society to which he was much attached, and by which he was greatly beloved. His conduct throughout his life was marked by the noble sentiments of a soldier, the courtesy and hospitality of a gentleman, and, above all, the real traits of a Christian. Few men have died more lamented, and none more deservedly. Long after his sepulchred remains, shrouded in general respect, shall have mouldered to the earth her due, will his memory survive embalmed in the public breast.Durham Chron. 19 Feb. 1836.
He left all his property to his wife; his personalty was sworn under a meagre £600.
