Prince Philip, Duke of Edinburgh, who has died at the age of 99, was the longest-lived consort of a British monarch who in her turn is the United Kingdom’s longest serving sovereign. It was a marriage of opposites – one a shy, introverted woman with a sheltered upbringing, while the other an outgoing, brusque man with a nomadic early life – but both The Queen and Prince Philip had a strong sense of duty and sought stability.