Task: Question Generation
Input (English): Passage: Candaules, King of Lydia, Shews his Wife by Stealth to Gyges, One of his Ministers, as She Goes to Bed, occasionally formerly known as The Imprudence of Candaules, is a 45.1 by 55.9 cm (17.8 by 22.0 in) oil painting on canvas by English artist William Etty, first exhibited at the Royal Academy in 1830. It shows a scene from the Histories by Herodotus, in which Candaules, king of Lydia, invites his bodyguard Gyges to hide in the couple's bedroom and watch his wife Nyssia undress, to prove to him her beauty. Nyssia notices Gyges spying and challenges him to either accept his own execution or to kill Candaules as a punishment. Gyges chooses to kill Candaules and take his place as king. The painting shows the moment at which Nyssia, still unaware that she is being watched by anyone other than her husband, removes the last of her clothes.
Etty hoped that his audience would take from the painting the moral lesson that women are not chattels and that men infringing on their rights should justly be punished, but he made little effort to explain this to audiences. The painting was immediately controversial and perceived as a cynical combination of a pornographic image and a violent and unpleasant narrative, and it was condemned as an immoral piece of the type one would expect from a foreign, not a British, artist. It was bought by Robert Vernon on its exhibition, and in 1847 was one of a number of paintings given by Vernon to the nation. The work retained its controversial reputation in later years, and when The Art Journal bought the reproduction rights to Vernon's former collection in 1849 they did not distribute reproductions of Candaules. In 1929 it was among several paintings transferred to the newly expanded Tate Gallery, where as of 2018 it remains.
Output (English): What is the last name of the man that bought the painting that was perceived as a cynical combination of a pornographic image and a violent and unpleasant narrative?