Military officer and Tory politician. Muncaster was a son of Sir Joseph Pennington, 4th Baronet, and Sarah Moore. Married (1778) to Penelope Compton (d. 1806).
Muncaster joined the military at an early age, enlisting in the 3rd Regiment of Foot as Ensign in 1756. In 1762, he was promoted Captain, and he rose further through the ranks to become Lt-Col in the 37th Regiment of Foot before his retirement in 1775.
In 1781, he was elected Member of Parliament for Milborne Port. He held this seat until 1796, before transferring to Colchester, which he represented until 1802. In 1806, he was returned for Westmoreland, and sat for the county until his death in 1813.
In 1783 Muncaster was also elected to the Peerage of Ireland as Baron Muncaster. Due to him and his wife having no male heirs, he was succeeded in the barony by his younger brother, Lowther (1745-1818).
Boswell and Dr Johnson met Lt-Col Pennington, as he then was, at Fort George on August 28, 1773, while on their tour of Scotland. They dined with the then commander of the Fort, Sir Eyre Coote, and several of his officers, including Pennington and Major Brewse of the Royal Engineers.