Prince Philip died of old age.
The Duke of Edinburgh passed away last month at the age of 99 and though he'd been in hospital for a procedure related to a heart condition just a few weeks before his death, his doctor didn't single out any specific contributory factor.
According to the Daily Telegraph newspaper, Sir Huw Thomas, the head of the royal medical household, listed "old age" as the cause of Philip's death on 9 April, an accepted description if the patient is over 80 and the doctor has personally cared for them a long time and observed a gradual decline.
It suggests there was no other identifiable disease or injury that contributed to the passing.
Philip's death was registered with the Royal Borough of Windsor and Maidenhead by his private secretary, Brigadier Archie Miller-Bakewell, four days after he passed away.
The document listed his full name as "His Royal Highness The Prince Philip, Duke of Edinburgh formerly known as Prince Philippos of Greece and Denmark formerly known as Philip Mountbatten."
His first listed occupation was Naval Officer and Prince of the United Kingdom, while his second was "husband of Her Majesty Queen Elizabeth II, The Sovereign."
Philip was described as having "passed away peacefully" when royal officials announced his death last month.
A statement read: "It is with deep sorrow that Her Majesty The Queen has announced the death of her beloved husband, His Royal Highness The Prince Philip, Duke of Edinburgh.
"His Royal Highness passed away peacefully this morning at Windsor Castle.
"Further announcements will made in due course.
"The Royal Family join with people around the world in mourning his loss."
His funeral - which was attended by just 30 mourners in line with current guidelines on coronavirus - took place on 17 April.