The Queen has publicly backed the Duchess of Cornwall to become Queen consort when Prince Charles accedes to the throne.
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In a poignant message to mark the 70th anniversary of her own accession, Her Majesty renewed her 1947 pledge "that my life will always be devoted to your service," but urged the public to support her son and heir and his wife when her remarkable reign finally comes to an end.
The monarch, 95, said: "I remain eternally grateful for, and humbled by, the loyalty and affection that you continue to give me.
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"And when, in the fullness of time, my son Charles becomes King, I know you will give him and his wife Camilla the same support that you have given me; and it is my sincere wish that, when that time comes, Camilla will be known as Queen Consort as she continues her own loyal service."
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Until now, the Duchess of Cornwall was expected to be styled Princess Consort when her husband becomes King, a decision announced when the couple married in 2005.
The lesser title reflects a sensitivity towards public opinion, which was negative towards Camilla in the aftermath of the breakdown of the Prince's marriage to Diana, Princess of Wales.
But in the years since then, the Duchess has weathered the storm and worked hard to earn widespread respect and admiration for her charitable work and loyalty to the royal family.
Her Majesty shared her wishes for the Duchess of Cornwall to take the title of Queen Consort
In her message, which was signed "Your servant, Elizabeth R" at Sandringham on the eve of her historic milestone, the Queen also paid tribute to her parents, her family and her late husband the Duke of Edinburgh.
She said of the 6 February anniversary: "It is a day that, even after 70 years, I still remember as much for the death of my father, King George VI, as for the start of my reign."
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She added: "I am fortunate to have had the steadfast and loving support of my family.
"I was blessed that in Prince Philip I had a partner willing to carry out the role of consort and unselfishly make the sacrifices that go with it. It is a role I saw my own mother perform during my father's reign."
The Prince of Wales married Camilla in 2005
Saying she looks forward to her Platinum Jubilee year "with a sense of hope and optimism", she added: "I am reminded of how much we can be thankful for."
She concluded by saying: "I look forward to continuing to serve you with all my heart," adding, "I hope this Jubilee will bring together families and friends, neighbours and communities – after some difficult times for so many of us – in order to enjoy the celebrations and to reflect on the positive developments in our day-to-day lives that have so happily coincided with my reign."
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National celebrations will mark the Platinum Jubilee later this year, culminating in a four-day Bank Holiday weekend in June.
But the Queen will spend her anniversary privately at Sandringham, where her father, who had been treated for lung cancer, passed away in the early hours of 6 February 1952.
The-then Princess Elizabeth was in Kenya on a Commonwealth tour with the Duke of Edinburgh and on hearing the news, immediately returned to London, where she was officially proclaimed Queen the following day.
The news will please Prince Charles
HELLO's royal editor Emily Nash says: "Royal watchers have long expected some kind of announcement that Camilla will one day be styled Queen Consort and having the Queen publicly give her seal of approval is a very elegant way of doing it.
"The future King has always been determined to make her his Queen and it makes total sense to clarify the decision before his own accession to the throne.
"The Queen’s message is a very poignant one, however, as she looks forward to a time when she is no longer monarch. At the age of 95 and after 70 years on the throne, this feels like she is putting her affairs in order."
A spokesman for the Prince of Wales said that he and the Duchess of Cornwall are "touched and honoured by Her Majesty’s words".
The heir to the throne is expected to be among the many public figures to pay tribute to the Queen on her anniversary.
The Duke and Duchess of Cambridge reacted to the news
In reaction to the news, the Duke and Duchess of Cambridge retweeted the Queen's royal message on their Twitter feed.
Likewise Clarence House, which is the official account for the Prince of Wales and Camilla also shared the message with no additional commentary.
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