The Duke of Marlborough, Savior of Blenheim Palace, Has Died at Age 88. The Duke of Marlborough, Savior of Blenheim Palace, Has Died at Age 88. Blenheim Born: 13 April, 1926, at Blenheim Palace. Died: 16 October, 2014, at Blenheim Palace, aged 88. The title, the Duke of Marlborough, was Kate Sheridan is at Blenheim Palace to research King Henry's mistress Rosamund, said to have been poisoned there Eleanor of Aquitaine. But her visit takes a strange turn when her hosts unwittingly begin to relive the legend. Not