We first started seeing more of each other when Philip went for a two-year job to the RN Petty Officers’ School at Corsham – before that we hardly knew each other. He’d spend weekends with us, and when the school was closed he spent six weeks at Balmoral – it was great luck his getting a shore job first then! We both love dancing – we have danced at Ciro’s and Quaglino’s as well as at parties.

She said of her engagement ring: ‘I don’t know the history of the stone, except that it is a very fine old cutting. It was given to me not long before the engagement was announced.’

She also wrote: ‘Philip enjoys driving and does it fast! He has his own tiny MG which he is very proud of – he has taken me about in it, once up to London, which was great fun, only it was like sitting on the road, and the wheels are almost as high as one’s head. On that one and only occasion we were chased by a photographer which was disappointing.’

The engagement ring was made by the jewellers Philip Antrobus of Old Bond Street using diamonds from a tiara belonging to Philip’s mother, Princess Alice of Greece. Philip designed it himself using a 3-carat diamond solitaire as a centrepiece, flanked by five smaller diamonds on each side, all set in platinum. The wedding band was made from a nugget of Welsh gold that came from the Clogau St David’s mine, near Dolgellau.

Although Philip had been a guest at Windsor Castle several times when Princess Elizabeth was a child, their romance may never have blossomed had it not fallen to him to escort the thirteen-year-old Princess Elizabeth and her younger sister Margaret around Dartmouth Naval College in July 1939. The royal family were on an official visit on the royal yacht Victoria and Albert. The Court Circular for that day reads: ‘His Majesty the King and Her Majesty the Queen, Her Royal Highness Princess Elizabeth and Her Royal Highness Princess Margaret visited the Royal Naval College, Dartmouth. Captain Lord Louis Mountbatten RN was in attendance.’

The plan had been for the family to attend morning chapel at the college, but because there had been an outbreak of mumps and chicken pox among the cadets it was decided that the princesses should not attend the service. Philip’s uncle Dickie Mountbatten was present in his role as aide-de-camp to the King. There is little doubt that Mountbatten had more than a hand in ensuring that Philip was picked over the other cadet captains to look after the princesses during the chapel service, as his dynastic ambitions had few bounds.