The Princess of Wales has access to the most incredible jewels within the royal vaults, and we've seen Kate borrow personal pieces that were once worn by the late Queen Elizabeth II and the late Queen Mother.
Speaking about the ring, Prince William said in their engagement interview in 2010: "I had been carrying it around with me in my rucksack for about three weeks before that and I literally would not let it go, everywhere I went I was keeping hold of it because I knew this thing, if it disappeared I would be in a lot of trouble and because I'd planned it, it went fine.
"You hear a lot of horror stories about proposing and things going horribly wrong - it went really, really well and I was really pleased when she said yes."
He added: "It's my mother's engagement ring so I thought it was quite nice because obviously she's not going to be around to share any of the fun and excitement of it all - this was my way of keeping her close to it all."
Kate said the precious jewel was "beautiful" and "very, very special". Take a look back at some of the most jaw-dropping royal engagement rings over the years in the video below...
In the 12 years that Kate has been a member of the royal family, we've seen her debut jewellery from Diana's collection, including tiaras, earrings and bracelets.
Take a closer look at all of Diana's jewels that Kate has worn in public…
Sapphire and diamond engagement ring
William proposed to Kate with Diana's diamond and sapphire engagement ring
The Princess recently divulged new information about her famous engagement ring.
When royal fans spotted the ring on Kate's left hand during her appearance in Wales – as part of her visit to celebrate the 60th anniversary of Central Beacons Mountain Rescue – she explained: "Same ring! And it's exactly the same size, it's very special. I'm honoured to wear it, I never sadly got to meet her.
However, instead of breaking and resoldering the band itself, the Princess found a way to have the ring resized without tampering with the original design – and it's completely reversible. Jeweller G. Collins and Sons added small platinum beads inside the band to reduce its diameter, which is why the secret alteration has not been visible from the exterior.
Lover's Knot Tiara
The Lover's Knot tiara is Kate's go-to
Kate has worn the sparkling diamond and pearl headpiece on more than ten occasions. The tiara was given to Diana as a wedding gift from the Queen in 1981 and Kate first wore it in December 2015 for the Diplomatic Reception.
Diamond and Sapphire Earrings
Kate wearing a modified version of Diana's sapphire and diamond earrings
The Collingwood Pearl and Diamond Earrings
Kate wearing Diana's Collingwood Pearl earrings
Kate first wore Diana's Collingwood pearl and diamond earrings at the Spanish state banquet in 2017. The earrings were given to Diana as a wedding present from Collingwood jewellers, and she wore them for numerous balls and formal engagements, including during a tour of the US.
Diamond and South Sea Pearl Earrings
Kate recently wore Diana's diamond and South Sea earrings for the coronation
The Princess delighted royal fans when she wore Diana's Diamond and South Sea Pearl Earrings at the 2019 BAFTAs, alongside a one-shoulder Alexander McQueen gown. Kate has since worn the jewels at Royal Ascot, Remembrance Sunday, and for King Charles's coronation on 6 May.
Three-strand Pearl Bracelet
Kate wore Diana's pearl bracelet for the first time on the Germany tour in 2017
Kate debuted Diana's three-strand pearl bracelet during her and William's tour of Germany and Poland in 2017. It was designed by Nigel Milne in 1988 and Diana wore it with her Catherine Walker "Elvis" dress in Hong Kong in 1989.
Double-drop Sapphire Earrings
Kate wearing Diana's diamond and sapphire earrings at Trooping the Colour 2022
The Princess has an impressive collection of sapphire jewellery, and she wore Diana's double-drop earrings for the first time at Trooping the Colour in 2022. The late Princess of Wales famously wore the earrings at the Met Gala in 1996.