By Nicholas Witchell
Royal correspondent, BBC News
Prince Phillip has been the Queen's constant companion
He was the person who broke the news to his then 25-year-old wife that her father, the King, had died and that consequently she was now Queen.
Some 16 months later, at the Coronation service within Westminster Abbey in June 1953, Philip was the first layman - preceded only by the most senior churchmen - to pay homage to the newly-crowned monarch.
Philip knelt before his wife, placed his hands between hers, and pronounced these words: "Faith and truth I will bear unto you, to live and die, against all manner of folks. So help me God."
He then touched the crown upon the Queen's head and kissed her on the left cheek.
No other living husband has been required to make quite such a public declaration of loyalty.
And, arguably, no other living husband's performance has been monitored quite so closely and over quite such a long period of time as that of Prince Philip, Duke of Edinburgh.
Frustrations and limitations
Philip has now become the longest-serving royal consort in British history.
The 57 years and 70 days that have passed since the day of the Queen's accession mean that Philip has surpassed the record set by Queen Charlotte of Mecklenburg-Strelitz, wife of the 18th Century British monarch, George III.
Queen Charlotte's principal contribution to her adopted country was to endure her husband's periodic bouts of violent insanity, and to bear him no fewer than 15 children.
Measured against such a precedent, it might be said that Philip has had a comparatively easy time of it.
Yet any such suggestion would undoubtedly be dismissed by the man himself in the forthright style for which he is famous, or perhaps infamous.
And the fact is that the role of a male royal consort to a female British monarch is not necessarily an easy one.
His natural confidence - some would say arrogance - has made him very sure about his own abilities and opinions
It carries with it precisely the sort of frustrations and limitations which would test a husband with several times the tact and patience than the notoriously short-fused Philip.
The wife of a British King is automatically his Queen Consort - as, incidentally, Prince Charles is only too well aware, despite Clarence House's attempts to suggest that Camilla will merely be "Princess Consort".
But the husband of a British Queen who occupies the throne has absolutely no formal role.
Only once in recent British history has there been a limited exception to this.
It was when Queen Victoria decided, 17 years after her marriage to her cousin Albert of Saxe-Coburg-Gotha, to appoint him Prince Consort and to consult him fully about the matters of state that she had to deal with as sovereign.
Victoria's great, great granddaughter, Elizabeth II, has far too traditional an approach to monarchy to follow that example.
Philip may be "first husband" and have authority over domestic matters within the royal family but, constitutionally, he has no significance. He is there to support the Queen, but never in any sense to supplant her.
That has not always been easy for Philip. Indeed, in the early years of the Queen's reign he found this lack of a defined role very difficult.
He is naturally curious and interventionist. His own rootless childhood had made him extremely self-sufficient, and his natural confidence - some would say arrogance - has made him very sure about his own abilities and opinions.
That, and his experience as a wartime officer in the Royal Navy, meant that a clash with the stuffier members of the court at Buckingham Palace was inevitable.
Battle of wills
The tweedier elements of that court were extremely suspicious of him. They regarded him as brash and, frankly, as rather uncouth.
But, of course, no-one was closer to the Queen than he was.
The gaffes are legendary and they have on occasions caused the Queen embarrassment
A battle of wills ensued, with the Queen caught between a husband who was determined to make his views heard, and a well-entrenched team of courtiers who were determined that the advice which counted with the young monarch would be theirs.
It was a battle which Philip couldn't win. As Lord Brabourne, who married Philip's first cousin Patricia Mountbatten, told the author Gyles Brandreth for his book Philip and Elizabeth: "Philip was constantly being squashed, snubbed, ticked off, rapped over the knuckles. It was intolerable"
The degree of Philip's frustration was summed up in his often-quoted and characteristically colourful remark "I am nothing but a bloody amoeba".
But Philip dealt with the hurt that he undoubtedly felt.
There was a period of mild rebellion in the latter half of the 1950s which involved long lunches, stories of louche behaviour and several extended foreign trips, after which he appears to have accepted the restrictions of the position in which he found himself.
First and foremost, he has been the Queen's greatest supporter.
He is easy to caricature as boorish and rude, and few would challenge the suggestion that he has on occasions lacked the sensitivity that might be expected of someone in his position.
The gaffes are legendary and they have, on occasions, caused the Queen embarrassment.
But in a world of, at times, suffocating protocol, absurd flummery and toe-curling obsequiousness, Philip has been a plain-speaking breath of fresh air who, almost certainly, deserves a great deal more credit than he often receives for helping to steer the monarchy through a period of extraordinary change.
Inside that spiky exterior lies a shrewd mind which, Palace officials say, will always be the first to see any flaws in a proposed plan of action, and who is a great deal more sensitive than he might care for people to realise.
The pledge Philip made to his wife at the Coronation has been honoured
The latter, little-recognised characteristic emerged recently when the letters he wrote to Diana, Princess of Wales about the breakdown of her marriage to Prince Charles were published during the inquest into her death.
Prince Philip has made his own mark in several areas of British life, but his major contribution throughout the nearly 60 years he's spent as royal consort has undoubtedly been the constancy of his support for one of the most remarkable reigns in the country's history.
His own verdict? "I've just done what I think is my best", he once said, adding: "Some people think it's all right, some don't. It's just too bad: they'll have to lump it."
And the Queen's verdict? It was delivered in a speech marking their golden wedding anniversary. She said: "He has quite simply been my strength and stay for all these years."
Which would tend to suggest that the pledge Philip made to his wife at the Coronation has been honoured.
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