It is either platinum or white gold, and the centre diamond is an Asscher cut diamond which was estimated to be upwards of three carats.
At the time of the engagement David Christopher Allen, Creative Director of 77 Diamonds, told the Telegraph: “It is Art Deco in style with an octagonal halo of round diamonds surrounding what looks to be a 4 carat Asscher cut diamond. Asscher cut diamonds are step cut inside, which means there are fewer facets than standard shapes such as round or princess square cuts.
“This means that their clarity has to be of the highest quality and close to flawless to show off the beautiful structure of the diamond.”
The diamond alone was valued at £200,000.
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Kate Middleton’s engagement ring
Kate’s ring – a large sapphire surrounded by diamonds – was an heirloom, so technically it cost Prince William nothing.
However, it has huge value in terms of its sentimental worth – as it was Princess Diana’s engagement ring.
But how much would have Kate’s ring cost William?
The ring was originally bought for Lady Diana Spencer in 1981, and cost £28,500.
Royal weddings: Meghan, Kate, Eugenie and Diana
Who: His Royal Highness Prince Harry and Meghan Markle (now the Duke and Duchess of Sussex)
Where: St George’s Chapel, Windsor Castle
When: 19 May 2018, Berkshire
Dress: Meghan wore a dress designed by Clare Waight Keller for Givenchy. The white dress was made of silk and had a boat neckline. The veil was an incredible 16 feet long.
Tiara: The Duchess of Sussex chose the Queen Mary diamond bandeau tiara, made in 1932, with a flower brooch in the middle from 1893.
Cake: The cake was made by Claire Ptak, based in London. It was lemon and elderflower cake, decorated with peonies and buttercream icing.
Notable guests: A-list guests included James Corden, tennis player Serena Williams, the Beckhams, Sir Elton John, George and Amal Clooney and Carey Mulligan and Marcus Mumford.
Who: Princess Eugenie of York and Jack Brooksbank
Where: St George’s Chapel, Windsor Castle, Berkshire
When: 12 October 2018
Dress: Eugenie’s dress was made by Peter Pilotto and Christopher de Vos and had a full skirt, long sleeves and was ivory in colour. The dress has a low back designed to show Euegnie’s scar from scoliosis surgery, a cause she has spoken out about in the past and since the wedding.
Tiara: She wore the stunning Greville Emerald Kokoshnik Tiara, lent to her by the Queen. It has a huge emerald in the middle.
Cake: The cake had five tiers and was a red velvet and chocolate cake made by London-based cake designer Sophie Cabot.
Notable guests: Famous faces at the wedding included Robbie Williams, Naomi Campbell, Kate Miss, Jack Whitehall and Liv Tyler.
Who: Prince William and Kate Middleton
Where: Westminster Abbey, London
When: 29 April 2011
Dress: Kate wore a dress made by Sarah Burton for Alexander McQueen. The satin gown featured long lace sleeves. It had a nine foot train and the lace featured roses, daffodils, thistles and shamrocks.
Tiara: Kate borrowed the Cartier Scroll Tiara, now known as the Halo tiara. It was bought by the Queen’s father, the future King George VI, for his wife Elizabeth.
Cake: William and Kate opted for a traditional fruit cake with eight tiers. It was decorated with sugar flowers. William also had an additional chocolate biscuit cake was made from a Royal Family recipe.
Notable guests: Guests included family and friends of the couple, as well as members of the military and people who work with charities the pair support.
Who: Prince Charles and Lady Diana Spencer
Where: St Paul’s Cathedral, London
When: 29 July 1981
Dress: Diana’s gown was designed by Elizabeth and David Emanuel and had an enormous 25-foot train. The dress was ivory and featured lace. In typical 80s style the rather large dress had huge sleeves. The dress was badly creased during the carriage ride to the ceremony, as it was so large.
Cake: Diana and Charles had a number of cakes including a five-foot-tall layered fruitcake. Another cake was made by Belgian pastry chef S. G. Sender and another by Chef Nicholas Lodge.
Notable guests: Guests includes foreign royals from Spain and Greece, as well as First Lady Nancy Reagan who represented the United States.