Prince Philip: Could he have become First Sea Lord?

Prince Philip served in the Royal Navy for more than a decade, including during the Second World War.

During his time in the British military, he was promoted to Lieutenant Commander, before ending his active naval career in July 1951.

In 1952, the Queen promoted him to Commander, prior to awarding him honorary five-star ranks across the tri-services the following year.

Philip's grandfather, Prince Louis, was Admiral of the Fleet and First Sea Lord, but how far up the naval ranks would the Duke of Edinburgh have progressed had he not ended his active service aged 30?

Prince Philip himself admitted to wondering how far his military career could have progressed, had fate not intervened.

The Duke of Edinburgh joined the Royal Navy in 1939, although admitted his uncle, Lord Mountbatten, played a part in that choice, with Philip also considering joining the Royal Air Force.

The Duke said in 1970 that he would have "without a doubt" joined the RAF had he made the decision alone, however later, in 1995, he recalled: "I think, left to my own devices I think I probably would've signed up for the Navy," during an interview with Richard Astbury.

"I was eventually persuaded by my uncle, Lord Mountbatten, that it might be more sensible to go into the Navy."

Writing in 'The Duke', biographer Tim Heald says: "When he took [his naval] exam he passed 16th out of thirty-four successful candidates; perfectly adequate but not at first glance the stuff of which First Sea Lords are made."

However, in the interview portion of his entrance assessment, Philip stood out, scoring 380 out of 400 marks.

Watch: Prince Philip recalls his military career and the Second World War.

He went on to graduate as the best cadet in his class from Dartmouth's Royal Naval College.

Philip was following family tradition in joining the Senior Service, with numerous relations having also served at sea.

"If I joined the Air Force, I wouldn't be here now," the Duke added, suggesting he may not have survived the war had he joined the RAF.

However, Prince Philip was safe from danger during his time at sea during World War Two.

He recalled in 1995 being on board HMS Valiant when "the whole ship bent" after a series of bombs hit, and was mentioned in dispatches for his efforts in the Battle of Cape Matapan while serving on the vessel.

Writing to Tim Heald in 1990, the Duke of Edinburgh admitted: "There has never been an 'if only', except perhaps that I regret not having been able to continue a career in the Navy."

Lord Lewin, who went on to be First Sea Lord and Chief of the Defence Staff, went one step further in the 'if only' hypothesising.

He once said that had Prince Philip continued his active service in the Navy, it would have been Philip who became First Sea Lord, and not himself.

Meanwhile, Admiral Sir Mark Stanhope, who was First Sea Lord from 2009 to 2013, said: "I think there’s little doubt if he remained in the Navy he would’ve been a very, very strong contender to rise to the top and be future First Sea Lord."

The Duke, when discussing the suggestion, said: "I never imagined that I would reach such dizzying heights as my uncle [Lord Mountbatten] or Lewin."