Ickworth, with its impressive central rotunda, was built by the 'Earl-Bishop', Frederick (1730–1803), 4th Earl of Bristol and Bishop of Derry, and was finally made habitable for the 1st Marquess between 1821 and 1832. It was transferred to the National Trust in 1956, having been accepted by HM Treasury in lieu of death duties together with most of its contents.
It has a fine picture collection, including many high quality family portraits by Angelica Kauffman, Pompeo Batoni, Hugh Douglas Hamilton, Madame Vigée-LeBrun, and Johann Zoffany. The earliest is a 1564 Anglo/Flemish School portrait of Francis Hervey (1534–1601/1602), in his uniform as one of Elizabeth I's Band of Gentlemen Pensioners. The collection was really begun by John Hervey (1665–1751), 1st Earl of Bristol, who sat for both a local artist John Fayram and the fashionable Frenchman Jean-Baptiste van Loo. William Hogarth's 'The Hervey Conversation Piece' celebrates Hervey with his circle of friends in a relaxed but enigmatic fashion.