Mark Singleton was born in 1762 to an Irish legal family, but looked to the army for a career over the law.
In 1785 Singleton married Lord Cornwallis’s daughter and became dependent on his father-in-law’s patrongae. In 1795 Singleton accepted the post of Ordnance Storekeeper offered to him by Lord Cornwallis, who was Master General of the Ordnance at the time. From 1796 Singleton also became more involved in politics under Cornwallis’ direction. In 1807 Singleton was restored to the post of Principal Storekeeper at the Ordnance, a post he had held briefly in 1799.
He remained in this post until 1829, even though he retired his seat in Parliament in 1820. He died 17 July 1840.