The Duchess of Edinburgh sparked a royal fan frenzy over her "sweet tribute to Prince Edward".
Sophie, 59, and the Duke of Edinburgh, 60, represented King Charles by attending a historic Changing of the Guard ceremony.
The duke and duchess accompanied France's Gendarmerie's Garde Republicaine to commemorate the 120th anniversary of the Entente Cordiale.
This was the historic diplomatic agreement between Britain and France.
The Duchess of Edinburgh wearing the same earrings in 2009
Getty
It further laid the groundwork for their collaboration in both world wars.
Sophie made a sentimental nod to her husband during the ceremony through her jewellery, opting for a pair of glittering aquamarine floral earrings.
The jewels are of particular significance to Prince Edward and Sophie, as the duchess was first spotted wearing the earrings for an engagement to mark their 10th wedding anniversary.
Sophie opted for the floral jewels when she visited Whitton School back in June 2009, a decade on from the couple's wedding in Windsor.
Sophie wore aquamarine floral earrings earlier this week
Reuters
Some royal watchers have even speculated that the floral gems could have been a gift from the duke to the duchess.
Fans went into a frenzy on social media over the beautiful jewels.
One wrote: "The Duchess of Edinburgh's beautiful aquamarine earrings look like Forget-Me-Not flowers."
Another said: "For some reason, I'm fangirling over the earrings… Very elegant and understated!"
Duchess of Edinburgh wore the earrings on her 10th wedding anniversary in 2009
PA
A third commented on the couple, saying: "The Edinburghs look lovely and stately."
A royal watcher added: "Sophie looks amazing as always. Such a wonderful, dignified and loyal couple."
The touching tribute from Sophie to her husband comes as the couple have often professed their love for each other in public recently.
During a trip to Leeds last month, Sophie said: "He has been my guide and shown me the way over the years.
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Duchess of Edinburgh's full outfit at the Changing the Guard ceremony
Reuters
"He has given me much help and advice (not always taken I admit), and his knowledge and instincts that have been honed over decades of service are invaluable - so we share speech notes (not this one, sorry darling!), chat through issues our patronages may be tackling, and together I think we make quite a good team."
Meanwhile, Prince Edward paid tribute to Sophie as his "absolute rock" with Alan Titchmarsh during an appearance on Love Your Weekend.
The duke said: "She's been an absolutely brilliant rock and I'm incredibly lucky that I found Sophie and that she found me.
"Hopefully we've been a really brilliant partnership. We're very lucky, we’ve got two, of what we would think are particularly brilliant children, who are forging such different paths for themselves. I think that's also equally fascinating."