Lorna Haddon, head of diamonds and jewellery at Beaverbrooks, explained: “This breath-taking engagement ring holds a stunning 12-carat oval blue sapphire, surrounded by fourteen smaller solitaire diamonds.

“The sapphire and diamonds are set in a slim 18-carat white gold band, which accentuates the central piece and draws the eye in to those incredible stones.

“A family heirloom, Kate’s ring once belonged to Prince William’s mother, Princess Diana, and has incredible sentimental value to the Prince.

“William explained that by Kate wearing his mother’s engagement ring, he felt that Diana was with them on their wedding day.”