[3] In July 1830 he was sworn of the Privy Council[4] and appointed Vice-Chamberlain of the Household in the Duke of Wellington's Tory administration.

[9] He sat in the House of Lords at Westminster for three years under this title before succeeding his father in the marquessate in 1844.

Lord Donegall married Lady Harriet Anne Butler (d. 1860), daughter of the 1st Earl of Glengall, in 1822.

Lord Donegall died in Brighton, Sussex, in October 1883, aged 86, and was buried in Belfast.

[1] As both his sons had predeceased him, the larger part of the Donegall estates was inherited by his only daughter, Harriet Ashley-Cooper, Lady Ashley (later Countess of Shaftesbury and previously Lady Harriet Augusta Anna Seymourina Chichester), wife of the 8th Earl of Shaftesbury.

[11] The Ennishowen and Carrickfergus barony died with him, while he was succeeded in his other peerages by his younger brother, Lord Edward Chichester.