Diamonds are forever! How necklace given to Princess Alexandra to mark her 1863 wedding was loved by Queen Elizabeth - and Camilla wore it at the State Opening of Parliament (on her birthday)

Last month's State Opening of Parliament was a special day for Queen Camilla in more ways than one.

As well as it being one of the most high-profile occasions of the year, it was Her Majesty's 77th birthday.

Given the majestic occasion, both she and King Charles were dressed to impress.

Whilst His Majesty wore the Imperial State Crown, it was Camilla who stood out in the Diamond Diadem, along with Queen Alexandra's Collet Necklace.

The latter piece is set with 31 graduated old-mine cut diamonds from the Golconda mine in India.

Queen Elizabeth II eventually inherited the antique and wore it on several occasions, including during a royal tour of Canada in 2010.

According to Hugh Roberts' encyclopaedic tome, The Queen's Diamonds, this remarkable piece (and the pair of earrings that are part of the demi-parure) were given to Alexandra by the City of London Corporation on her marriage to Bertie, Prince of Wales - latterly Edward VII - in March 1863.

Despite being rendered by hand, its diamonds are just as exquisite as anything cut today. 'Old mine cut diamonds beautifully showcase the artistry of 19th-century diamond cutting,' says Grant Mobley, Jewelry Editor of the, New York based, Natural Diamond Council.

Queen Camilla wore the Diamond Diadem  for the State Opening of Parliament last month. The occasion on her 77th birthday. She also wore Queen Alexandra's Collet Necklace. Above: Camilla in the Diamond Jubilee State Coach as it is pulled down The Mall towards Parliament, July 17, 2024

Her collet necklace could be worn as a choker and was a presented to the Danish Princess by the City of London Corporation on her marriage to  Bertie, the future Edward VII, in 1863

'They reflect a time when cutting was a true craft executed by nothing more than an artist's vision for the rough diamond.'

Five of its diamonds were detachable, allowing Alexandra to wear it as a choker, either by itself or attached to a velvet ribbon.

She often wore chokers or diamond dog collars to cover up a tiny scar on her neck that she sustained as a child.

The Diamond Diadem, also called the State Diadem, was created for King George IV's Coronation in 1821.

It has subsequently been worn (and slightly altered) by queens, both regnant and consort, including Queen Elizabeth II, who wore it for the first time for the State Opening of Parliament in 1952.

Queen Elizabeth II, wearing the State Diadem, on the way to Westminster to preside at the first State Opening of Parliament ceremony since her accession to the throne in 1952

Queen Elizabeth en route to Westminster Abbey for her Coronation Ceremony in 1953

The diamond Collet Necklace, worn by Queen Camilla, is set with 31 graduated old-mine cut Golconda diamonds and the dazzling diamond earrings. Also worn on her birthday, were part of what has become known as the Modern Diamond Suite

The Queen wore the diamond Collet Necklace when she attended the Royal York Hotel in Toronto, Canada at a dinner hosted by the Canadian Government in her honour  in 2010

She wore it again the following year on the approach to her own Coronation and then again for the journey to every State Opening during her 70-year reign.

It is set with 1,333 diamonds, including an exquisite cross at the front, with two bands of pearls around the diadem.

It is especially well-known because of the fact that its outline featured as part of the Queen's silhouette on postage stamps.

On her birthday Camilla also wore a dazzling pair of diamond earrings that are part of what has become known as the 'Modern Diamond Suite'.

It was made from diamonds originally set in a tiara that Charles bought at auction in 2005.

It comprises a necklace, set with marquise and oval diamonds, from which pear shapes are suspended; and the pair of earrings with a waterfall drop of pear-shaped diamonds.

But the Queen doesn't have pierced ears. She famously told British Vogue in 2023: '... nothing's going to pierce my ears.'

It means she has to wear clip-ons. I imagine that most of the Royal Collection's earrings can't be altered, so she wears these very frequently with different jewels.

Camilla's outing at the State Opening proved that diamonds, from ancient to new, really are forever – and a girl's best birthday friend!