Cressida Bonas' step-father died of a drug overdose.
Christopher Shaw was found dead at his rented home in Wiltshire in January and toxicology tests have now revealed the former banker's death was caused by an overdose on prescription pills.
Friends and family of Christopher, 76, were left devastated by his passing and faced several agonising weeks to find out how he died.
An inquest in Salisbury, Wiltshire, was told a post mortem examination had shown his death was not natural and he was found dead at the scene by his housekeeper Nicola Smith.
Christopher - who was once known for his millionaire lifestyle - was reportedly struggling with financial problems, but appeared to be in good spirits in the days leading up to his death as he had just returned from a holiday in Cuba.
He began dating Cressida's mother Lady Mary Gaye Curzon in 1994 and the pair were together for six years - four years as a married couple - before they divorced in 2000.
A friend said previously: "Cressida was five when they got together and 11 when it all went wrong so Christopher would have been a strong presence in her childhood life."
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