It was created in 1694 for the prominent statesman Thomas Osborne, 1st Marquess of Carmarthen, who had been one of the Immortal Seven in the Revolution of 1688.

[3] After Kiveton Hall was demolished in 1811, Hornby Castle became the main seat of the Dukes of Leeds.

[4] The traditional burial place of the Dukes of Leeds was All Hallows Church, Harthill, South Yorkshire.

[2] The 11th Duke was married three times; he had a daughter, Lady Camilla Osborne, but no son.

[8] Eight months later, the 12th Duke died in Rome, unmarried, at which point the dukedom and the Barony of Godolphin became extinct.