The Duke refused to see or support his son, especially after the child turned out to be a mere daughter. Eventually St. George fled to Paris, and begged a commission from his second cousin, Major Richard Wimsey, then in the French army. The booklet also contains letters from the Major's father, who would be heir to the dukedom if St. George died: one urging his son not to help him: if St. George were killed in the wars, "it wd. be the common talk thou wast no better than thy poor Cousin's Murtherer"; another telling how he provided the Duke with the unusual experience of hearing the truth to his face: that the marriage might not be mended and His Grace should make the best of it. There is also a sentimental narrative of the eventual reconciliation, by Horace Walpole.
Convinced at Cambridge of his predestined damnation, he spent 15 years in religious melancholy, until about the age of thirty-six he had a vision of "himself being drawn up in a great net out of the sea, together with a multitude of fishes" and a voice saying "Mine own will I bring again, as I did sometime from the depths of the sea" He retired joyously to a hut in the depths of the Wash. He spoke no words, swam persistently, wore nothing but a girdle of fish-skins, and ate only fish-food. He would avoid his own name, but was called old Scaley and Ichthus, or rather Ιχθυς.
Towards the beginning of June 1815, he was seen by three fishermen, standing on the shore gazing towards the rising sun. He said to them, "Have you seen Him? Have you seen Him?". After some confusion at hearing the dumb speak, they explained that they had seen nobody. "But can you not see our Lord Himself, walking on the water?" They could see nothing but the golden track of the sun's reflection, but the Hermit cried out: "Thou shalt open my lips, O Lord! The tongue of the dumb shall sing", plunged in, and swam towards the sunrise.
His body was recovered a week later, having been drawn out by a trawler "with an astounding multitude of fish, so that the net brake" He was given Christian burial, probably at Pakefield, Suffolk; the cemetery has washed into the ocean, so the sea has him.
The group also created some other material about that very Augustan figure, the 10th Duke, including his pompous funeral inscription by the Rector of Duke's Denver (which living was of course in the Duke's gift), and a charcoal sketch for his portrait.
Dorothy Sayers does not appear to have noticed this anomaly, nor did her friends; when the professional herald of the group wrote up the Wimsey arms as a spoof article after her death for a heraldry magazine, a correspondent wrote in with the objection. The herald, C. W. Scott-Giles, later published a book, cited below, on the family which includes an intricate explanation: Lord Peter and his brother are descended from two branch lines of Wimseys, and the title was recreated in 1820, after the death of the 12th Duke.
So the 10th Duke is a collateral ancestor in the male line, a distant cousin. However, the relationship is closer if we include descents through women; the Duke's great-aunt married Lord Peter's direct ancestor.
It may be closer still: The Duke's mother was a Death, like Lord Peter's grandmother (the "old family name" of Murder Must Advertise). Scott-Giles' reconstruction implies that both the Duke's daughters married and had children. Miss Sayers wrote about the inbreeding in Lord Peter's ancestry: it would be both likely and plausible that one of them married into the Deaths, the Delagardies, or one of the Wimsey lines; which would make the Duke Lord Peter's direct ancestor.