Prince Philip's cause of death has been confirmed by Sir Huw Thomas, the head of the royal medical household.

The Duke of Edinburgh passed away "peacefully" at Windsor Castle on April 9th, aged 99. According to the document (obtained by The Telegraph) which was certified by Sir Thomas, the duke died of "old age". Thomas identified that no disease or injury that could have contributed to his death.

"Old age" can be listed as a cause of death if the patient is over 80, and if the doctor in charge has taken care of the patient over a long period of time, during which they have observed a decline in their patient's health.

Philip's death was registered four days after he passed away, with the Royal Borough of Windsor and Maidenhead by his private secretary, Brigadier Archie Miller-Bakewell.

Buckingham Palace announced his death with the statement: "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. The Royal Family join with people around the world in mourning his loss. Further announcements will be made in due course."

The Duke retired from royal duties in 2017 at the age of 96 and carried out his last solo public engagement on 2 August 2017 when he met the Royal Marine Corp. He did however make several public appearances alongside the Queen since. Notably at the Duke and Duchess of Sussexes' 2018 wedding as well as at Princess Eugenie and Jack Brookbank's nuptials in October of the same year.

A ceremonial funeral was held for Philip at St George's Chapel at Windsor on April 17th, which was attended by 30 guests including the Duke and Duchess of Cambridge, the Duke of Sussex, and Princesses Eugenie and Beatrice.