He served as Joint Postmaster General and was for many years Chairman of Committees in the House of Lords.

He succeeded his father as 2nd Baron Walsingham on 9 May 1781 and inherited his Merton Hall, Norfolk estate from his uncle Thomas de Grey the same year.

His other public posts included Lord of Trade (1777–1781), Under-Secretary of State for the American department (February 1778 – September 1780), Vice-Treasurer of Ireland (1784–1787) and joint Postmaster General (1787–1794).

Walsingham sat as Member of Parliament for Wareham in 1774,[4] for Tamworth from 1774 to 1780,[5] and for Lostwithiel from 1780 to 1781,[6] when he succeeded his father and took his seat in the House of Lords.

He died in January 1818, aged 69, and was succeeded in the barony by his eldest son, George.