In August 1780 Sir Theodosius Boughton, a dissolute Old Etonian twenty-year-old and heir to a Warwickshire fortune, died in painful convulsions after taking his medicine. The following year after an inquest and trial which became a cause celebre, his brother-in-law, Captain John ‘Diamond’ Donellan, Irish soldier of fortune and man about town, was tried for his murder. The trial was a shambles. And was Donellan guilty? Based on extensive research and the engrossing trial transcripts Elizabeth Cooke’s book shows the dark and violent underside of the society of Mansfield Park.