[1] The peerage had been intended for Sir John in return for his support for the Union with the Kingdom of Great Britain.

The Blackwood family, originally of Scottish descent, were prominent landowners in County Down and controlled the borough constituency of Killyleagh in the Irish Parliament.

The latter's grandson, the fifth Baron, was a prominent Liberal politician, diplomat and colonial administrator, and notably served as Governor General of Canada and Viceroy of India.

Lord Dufferin and Ava also assumed by royal licence the additional surname of Hamilton in 1862 and that of Temple (which was the maiden name of his father's mother) in 1872.

[1] After his death in the Second World War, the titles were inherited by his six-year-old son, the fifth Marquess, later a well-known patron of arts.

[1] His widow, Lindy, Marchioness of Dufferin and Ava lived at the Clandeboye Estate until her death on 26 October 2020.