The Henley Poisoner

The Henley Poisoner

On a visit to Oxford Castle, I was particularly intrigued by the tragic story of Mary Blandy, who was executed for poisoning her father in Henley-on-Thames, which is close to where I live. Although this case took place in the 18th century (outside my historical comfort zone), I decided to investigate…



Mary Blandy was born in Henley, around 1720. Her father, Francis Blandy, was a successful lawyer and the town clerk. The family lived at 29 Hart Street (now a dental practice) in the town centre. Mary’s mother died about 1749, but by this time, Mary had already met her future husband.

Captain William Henry Cranstoun was a captain in the army. The son of a Scottish nobleman and some 20 years her senior, he had met Mary when his regiment was in the district. The couple fell in love and planned to marry, but there was one major obstacle: William already had a wife. Captain Cranstoun returned to Scotland several times to try to have his marriage dissolved and, in the meantime, he sent letters and packages to Mary, whose father disapproved of the match.

In August 1752, Francis Blandy fell ill, complaining of bowel pain, a sore throat and ‘a stench in his nose’. As his condition worsened it became apparent that his daughter had been adding a white powder to his porridge. The powder had come from her lover, Captain Cranstoun, who had sent her ‘Scottish powder’ to clean some pebbles that he had given her to be set into earrings. It is unclear why Mary was adding the powder to her father’s food, and it has been suggested that she believed it to be a love potion, to endear him to her unfavourable suitor. In fact, when Francis confided in his doctor that he believed he was being poisoned, he referred to Mary as a ‘poor love-sick maid’.



On 14 August, Francis Blandy died. Shortly after, his doctor warned Mary that she might be inculpated in his death and so she burned her letters and the powder from Captain Cranstoun. The package containing the incriminating powder was quickly removed from the flames by a member of the household staff and Mary was placed under house arrest. Contemporary press reports indicate that Captain Cranstoun was the real ‘contriver of this detestable murder’, his motive being Mary’s £10,000 (about £1.4 million today) inheritance, which would have passed legally to him on their marriage.

Mary Blandy was tried at the Oxford Assizes for her father’s murder on 3 March 1752. In the first case of medical evidence being used in a trial for murder by poisoning, Dr Anthony Addington, a fellow of the College of Physicians and local resident, testified that he had examined Francis’ organs and found powder which had the appearance of ‘white arsenic’ (there was no test for arsenic until 1836). Despite Mary’s protestations that she did not intend to kill her father, she was convicted and sentenced to death.



On 6 April 1852, which was Easter Monday, Mary Blandy mounted the scaffold near Oxford Castle. Dressed in black and described as ‘serene and composed’, she climbed the first five steps of the ladder and then stopped, saying, ‘Gentlemen, I beg that you will not hang me high, for the sake of decency.’ Placing a handkerchief over her face, she was hanged by the neck.

Mary’s body was placed in a coffin lined with white satin and buried alongside her parents in Henley-on-Thames Cemetery. There is no longer any trace of her grave, but Mary’s sad tale is re-told in the permanent exhibition at Oxford Castle.







  1. I enjoy your historical stories from in and around my home town tremendously.
    Thanks for sharing your work.

    • Thank you, Neil – I’m delighted that you enjoy my cases and it’s lovely to know.


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