Philip’s military career was truly central to his character, unlike perhaps other royals, according to Ashley Jackson, a professor of imperial and military history at King’s College London.

“It’s easy to look at the military career of a royal male and see it as a rite of passage, but with Philip one needs to look beyond that,” he said. “He joined when he wasn’t anywhere near marrying the future queen. This was a career path for a Greek prince,” he added. “This wasn’t a brief dalliance in the military. It’s important to note that he’s clearly an exceptional officer.”

Then known as Philip Mountbatten, he first met his cousin Elizabeth in 1934 at a family wedding. The two are both great-great-grandchildren of Queen Victoria.

The couple exchanged letters while Philip was overseas during the war, only occasionally seeing each other. They would go out driving in Philip’s “tiny MG” sports car, as well as dancing at London nightclubs.