 Claiming falsely to have been ordained by Thomas O'Beirne, Bishop of Ossory, Halloran afterwards became a chaplain in the navy, and in 1805 was on the "Britannia" at the Battle of Trafalgar.The following year, he was posing as a clergyman in Bath In 1807 he was at the Cape of Good Hope as a chaplain to the forces.In 1811, now also holding a school principal's position, he interfered in a duel between two officers and was removed to Simon's Town.