Duchess Catherine's necklace is a subtle nod to Princess Diana.
The 35-year-old royal was given a piece of jewellery designed London boutique Merci Maman by her sister Pippa Middleton to mark the birth of her first child, Prince George, now four, and is a poignant mark of respect to her late mother in law.
Writing in their blog on the Merci Maman page, they shared: "Alongside the iconic fashion of Princess Diana's wardrobe went her wonderful collection of jewellery. Family was one of the closest things to Diana's heart so it's no surprise that this shone through in her jewellery, featuring personalised pieces and meaningful charms.
"The young Lady Spencer owned a simple gold chain bearing her initial 'D', keeping her early jewellery minimal and personal. Upon the birth of Prince William in 1982, Prince Charles gave Diana the gift of a gold pendant engraved their new son's name, which she always wore close to her heart.
"In 2013, Pippa Middleton continued this family tradition by giving her sister Kate, The Duchess of Cambridge, our Personalised Duchess Necklace to celebrate the birth of Prince George. Featuring a hand-engraved disc with the Prince's full name, a small boy charm and a heart engraved with a 'W' to represent Prince William."
It is not the first time Catherine - who also has Princess Charlotte, two, with her husband Prince William - has used jewellery as a royal tribute to Princess Diana.
To finish her tour of Berlin recent, Duchess Kate opted for a beautiful pearl bracelet belonging to Princess Diana.
The bracelet was designed by Nigel Milne in 1988 and London-based jeweller Milne wrote on his website: "I am delighted to see in the national press that the Duchess of Cambridge chose to wear one of her late mother-in-law's favourite pearl and diamond bracelets on the Royal Tour in Germany last week. This is of particular interest to me in that it was designed by me and featured in our 1988/1989 jewellery catalogue ...
"This is the bracelet that Princess Diana wore on several occasions including at the Birthright Ball in 1989 and with her iconic Catherine Walker 'Elvis' dress in Hong Kong and has now been seen adorning the Duchess of Cambridge!"