[1] Brudenell was born in London, England, the second son of George Brudenell, 3rd Earl of Cardigan, by Lady Elizabeth Bruce, daughter of Thomas Bruce, 3rd Earl of Elgin.

[3] Brudenell was Member of Parliament for Shaftesbury from 1754 to 1761,[3][4] for Hastings from 1761 to 1768,[3][5] for Great Bedwyn from March to November 1768[3][6] and for Marlborough 1768 to 1780.

[3][7] He served as Deputy Cofferer of the Household from 1755 to 1760, as Master of Robes to the Prince of Wales from 1758 to 1760, who acceded as King George III, and as Keeper of the Privy Purse from 1760 to 1811.

In 1791 he was appointed Constable and Governor of Windsor Castle (succeeding his brother the Duke of Montagu), a post he held until his death.

The Countess of Cardigan died at Seymour Place, Mayfair, London, in June 1823, aged 65.