The judge resumes his summing up with Philip Boyes’s final days. On June 22 his skin peeled from his lips, and in front of his father and Nurse Williams he said: ‘Harriet will be rid of me now. I didn’t know she hated me quite so much.’ He died at three in the morning on June 23, and the doctors, finding the symptoms matched his old gastric trouble, signed a certificate of acute gastritis. It was Nurse Williams’s gossip in the Bloomsbury literary set that set the rumour of arsenic moving, until Ryland Vaughan pushed the case, Norman Urquhart consulted Dr. Weir, and an exhumation followed.

Sir James Lubbock’s analysis found arsenic throughout the organs and calculated a fatal dose of four or five grains taken about three days before death. The defence argued Boyes poisoned himself during the ten unexplained minutes between leaving Doughty Street and hailing a cab, but no one could show he ever had arsenic. Worse for Harriet, arsenic near the roots of his hair pointed to poisoning months earlier. When police first told her, she laughed and said she was writing a book all about arsenic poisoning.

• How onset times after arsenic range from a quarter of an hour to seven hours, and why an empty stomach matters
• The missing charcoal or indigo that commercial arsenic is legally required to contain
• The judge explaining arsenic moving up a hair shaft by comparing it to a growing out permanent wave
• Harriet’s claim that she burnt all her poisons before the end of May, and her shelf of Madeleine Smith, Seddon, and Armstrong trial reports
• Lord Peter Wimsey’s verdict on the judge: ‘A beast, but a just beast’