Prince William and Princess Kate share sweet birthday tribute to Queen Camilla

The Prince and Princess of Wales joined Queen Camilla's birthday celebrations by sharing a sweet message on Instagram on Monday.

Prince William and Kate posted a photo of the Queen with their 15 million followers on Instagram Stories on Monday, writing: "Happy Birthday to Her Majesty the Queen."

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The photo was taken from Queen Camilla's visit to Wimbledon on Wednesday, where she was joined by her sister, Annabel Elliot, to watch the action on centre court.

Prince William and Kate weren't the only royals to publicly wish Camilla a happy birthday; messages were also shared by the Royal Family and on King Charles and Camilla's official Instagram account, which posted three photos of the monarch, writing: "Wishing Her Majesty The Queen a very Happy Birthday today!"

Camilla turns 76 on Monday, and the occasion marks her first birthday since becoming Queen. To celebrate the special day, a 41-gun salute by The King's Troop Royal Horse Artillery Battery took place at London's Green Park at midday, just a short distance from King Charles and Queen Camilla's royal residences of Buckingham Palace and Clarence House. It was the Queen's first official gun salute since her husband acceded the throne in September.

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The birthday celebrations followed a busy week of engagements, including Camilla's surprise visit to Wimbledon, and her joint visit to St Ives with King Charles on Thursday.

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However, the royal couple will soon be able to enjoy some downtime together as they are expected to start their summer holidays in the coming weeks. It is expected that King Charles and Camilla will continue their custom of spending the first week of August at the Castle of Mey – the former home of his late grandmother – before heading to Birkhall, their home on the Balmoral estate.

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Currently, work is being carried out within the grounds of Balmoral Castle and it will remain open until mid-August, meaning the royals will likely spend less time there this summer than they typically would during Queen Elizabeth II's reign.