The ring belonged to Princess Diana
Prince William proposed to wife Kate Middleton in 2010, and popped the question with his late mother's sapphire ring.
However, the Duchess of Cambridge has had to alter the bejewelled item, which is made from 12-carat oval blue sapphires circling a 14 solitaire diamond, in fear it would fall off and she would lose it.
It was reported in 2011, just before her wedding to the Duke of Cambridge - who have sons Prince George, Prince Louis and daughter Princess Charlotte together - had to get the engagement ring altered because it was "turning on her finger".
It has been claimed the 40-year-old took the ring to the jewellers G Collins and Sons, who made the adjustment.
Get the look: Kate Middleton's engagement ring:
However, instead of resizing the band, and removing any of the precious metal or gems, an adjustment was made to the bottom of the band so the original was still in tact.
The experts are said to have attached small platinum beads inside the bottom of the ring to make it fit Kate's finger.
A source told The Sun Online: "A bride's worst nightmare is looking down and seeing her ring has fallen off.
"One can only imagine how this is magnified when you are marrying the future King of England."
The engagement ring is joined by Kate's wedding band, which is made from Welsh gold, as well as a third ring.
However, the sapphire engagement ring almost didn't make it on to Kate's finger.
The heirloom was said to be passed down to Diana's youngest child Prince Harry, but Kate's brother-in-law reportedly "selflessly" gave up the ring for William to pop the question to Kate with.
Former royal butler, Paul Burrell, spoke about the sweet gesture on The Diana Story, and claimed Diana and Prince Charles' children were given permission to keep select pieces of their late mother's jewellery they wanted to remember her by.
But what did this mean for Prince Harry when he wanted to propose to Meghan Markle? He designed his very own creation.
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Maisie is a writer and editor, covering Royal News, Showbiz, Lifestyle content, as well as Shopping Writing and E-Commerce, for print and digital publications, including Marie Claire, Hello!, Fabulous, Mail Online and Yahoo!.
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