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Prince Charles, Prince of Wales and Camilla, Duchess of Cornwall, are photographed by Mario Testino in the Morning Room at Clarence House in May 2017 to mark the Duchess's 70th birthday Getty

Camilla, Duchess of Cornwall turns 70 today (17 July) and Clarence House have released an official photograph taken by one of Princess Diana's favourite photographers to mark the milestone.

The future Queen of England is pictured smiling widely next to here husband of 12 years, Prince Charles, 68, in the portrait picture.

Wearing a navy dress suit and a pearl necklace with matching pearl-drop earrings, Camilla looks at least ten years younger than her real age in the flattering photo, which was taken by Mario Testino in the Morning Room at Clarence House in May 2017.

Testino shot to worldwide stardom after taking a series of beautiful pictures of Diana for the Vanity Fair July 1997 issue – a month before she died.

Speaking about snapping Camilla for her 70th birthday, Testino said: "I'm honoured to document Their Royal Highnesses The Prince of Wales and The Duchess of Cornwall on this very important date.

"I first photographed The Duchess after her wedding to The Prince on a commission from British Vogue in 2006, and discovered a kind and beautiful person with a wonderful sense of humour.

"Doing this latest assignment to celebrate Her Royal Highness's 70th birthday is a true honour," he added.

Camilla celebrated becoming a septuagenarian with two parties over the last week and held a garden party for her staff and her many charities on Thursday at Clarence House in London.

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Princess Diana's Vanity Fair cover www.vanityfair.com

Her step-sons Princes William and Harry attended along with her own children Tom Parker Bowles and Laura Lopes. Camilla's ex-husband Andrew Parker Bowles also made an appearance, and despite his many affairs during their failed marriage from 1973-1995, they remain good friends.

Camilla's public image has no doubt improved in recent years, and it's clear to see that she makes Charles very happy. The couple were in a relationship before, during and after their former marriages, with Camilla being described as the 'third person' in Charles' and the late Diana, Princess of Wales' marriage.

Camilla's relationship with Charles has attracted worldwide scrutiny, but the pair finally wed in 2005 after years of controversy at Windsor Guildhall.

Ahead of her 70th birthday, an explosive biography about Camilla's life written by Penny Junor was released in extracts, claiming that Diana menaced her before two television interviews which rocked the monarchy.

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The Duchess of Cornwall and Prince of Wales have a drink at The Bell Pub in Purleigh during an official visit to Essex Getty

Junor made the astonishing claim that Diana confronted Camilla publicly at a party about her relationship with Charles and left a chilling message on her answer phone which said: "I've sent someone to kill you. They're outside in the garden. Look out of the window; can you see them?"

Camilla is said to not have been angry towards Diana as some might expect, and was instead sympathetic towards her. But she also couldn't forgive the princess for deliberately saying things to "damage Charles".

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A young Diana relaxes with Prince Charles in a loose pink dress and matching hat with bow detail during their first official Australian tour together in 1983. Getty