Crimes: Murder of his wife, Veronica Bonnar, and her mother, Lady Mary Menzies, in their home in Ealing, London.
He also appeared in court at the age of 17, for the murder of his mother Bertha Merrett in 1926 in Edinburgh. The verdict for this was " not proven".
Method: He got his wife drunk on gin and then drowned her in the bath. His mother-in-law was hit over the head with a coffee pot and strangled.
Sentence: Merrett committed suicide on 16th February 1954, shooting himself in the head.
Interesting facts: Merrett's mother was at first presumed to have committed suicide - she died from a single gunshot behind her ear. After her death though, it became apparent that Merrett had been defrauding her for quite a while and had a strong motive to kill her. The forensic evidence was reconsidered in the light of this. At the trial, there was great discussion as to whether the ballistic evidence could show that she had not committed suicide, but been shot.
After the verdict of not proven, and his imprisonment for the related offence of uttering a false cheque, Merrett married Bonnar. In 1921 he inherited �50,000, giving �8,400 of it to his wife. He also changed his name to Ronald Chesney. After the war, he dealt goods on the black market. When his money finally ran out, he decided to kill his estranged wife to get back the money he'd given her.
Bloodstains and hairs found on the clothes of Merrett after his death linked him to the murder of his wife and mother-in-law. An inquest decided that he had unlawfully killed them both.