On the evening of March 18, 2026, the Princess of Wales once again proved why she remains one of the most stylish and symbolically astute members of the British royal family. At the first state banquet of the year, held at Windsor Castle in honour of Nigerian President Bola Ahmed Tinubu and First Lady Oluremi Tinubu, Princess Catherine (Kate Middleton) made a radiant entrance in a striking emerald green gown, accessorised with a piece of royal history closely associated with her late mother-in-law, Princess Diana.

The occasion marked a significant diplomatic event, with King Charles III and Queen Camilla hosting the Nigerian delegation. Prince William and Princess Catherine played key supporting roles, helping to welcome the guests in St George’s Hall. While the green dress paid elegant tribute to Nigeria’s national flag, it was Catherine’s choice of jewellery — particularly the iconic Queen Mary’s Lover’s Knot Tiara — that sparked headlines about a “heartfelt tribute” to Diana.

The Flawless Green Gown: Diplomacy Through Fashion

Catherine’s ensemble was a bespoke or reworked high-necked gown by designer Andrew Gn, featuring dramatic billowing sheer sleeves and a flowing chiffon silhouette from the label’s autumn/winter 2021 collection. The deep forest-emerald shade perfectly echoed the vibrant green of Nigeria’s flag, a classic example of royal “sartorial diplomacy” that Queen Elizabeth II and other senior royals have long employed.

The conservative neckline and long sleeves also showed cultural sensitivity, respecting traditional expectations during the state visit. Paired with satin Manolo Blahnik heels and a silver Jenny Packham clutch, the look was both regal and modern — described by fashion observers as “flawless,” “dazzling,” and “the belle of the ball.”

This was not Catherine’s first time using colour to honour a visiting nation. She has repeatedly demonstrated a keen understanding of how fashion can convey respect and warmth on the global stage, and the Nigerian state banquet offered another masterclass in thoughtful dressing.

A Sparkling Nod to Princess Diana

The standout element for many royal watchers was Catherine’s choice of headpiece: Queen Mary’s Lover’s Knot Tiara. Originally created in 1913, the delicate diamond and pearl tiara has a strong emotional connection to Princess Diana, who wore it frequently during her time as Princess of Wales. Catherine has made it her signature choice for major state occasions, wearing it multiple times in previous years, including for U.S. and French state banquets.

By selecting this particular tiara for the 2026 Nigerian banquet — her first tiara appearance of the year — Catherine subtly honoured her husband’s late mother. The piece, often called one of Diana’s favourites, carries layers of royal continuity. Many outlets framed the moment as a “heartfelt tribute,” noting how Catherine has increasingly embraced items and styles linked to Diana while carving out her own identity as the future Queen.

She completed the jewellery with sapphire and diamond fringe tassel earrings from the late Queen Elizabeth II’s collection, adding another layer of heritage and sparkle. Earlier in the state visit, Catherine had also worn pearl earrings associated with Diana, reinforcing the theme of quiet familial remembrance.

A Poised Return to the Spotlight

The state banquet came at a time when Catherine has been steadily increasing her public engagements following her 2024 cancer treatment and recovery. Her appearance radiated confidence and elegance, with the Princess looking relaxed and radiant alongside Prince William. The couple supported the King and Queen Camilla throughout the glittering evening, which included formal toasts, fine dining, and diplomatic conversations.

Royal fans and commentators flooded social media with praise. Descriptions ranged from “stunning princess moment” to “timeless elegance,” with many highlighting how the combination of the green gown and Diana’s tiara created a perfect blend of diplomacy, tradition, and personal meaning.

Fashion experts noted the gown’s dramatic sleeves and ruching details, which added movement and sophistication under the lights of St George’s Hall. The overall effect was one of effortless glamour — a reminder of Catherine’s ability to balance high fashion with royal protocol.

Beyond the Gown: Symbolism and Continuity

This appearance fits into a broader pattern for the Princess of Wales. She has long used clothing and accessories to tell stories — honouring hosts, remembering predecessors, and signalling continuity within the monarchy. Wearing the Lover’s Knot Tiara while dressed in diplomatic green was widely seen as a graceful way to connect past and present: paying respect to Diana’s legacy while embracing her own role as a modern royal consort.

The event also underscored the Waleses’ growing prominence in state affairs as they prepare for the future. With Prince William increasingly involved in key initiatives and Catherine continuing her work in early childhood, mental health, and the arts, moments like this state banquet highlight their partnership and poise under pressure.

A Night to Remember

Princess Catherine’s flawless green gown and sparkling tribute to Diana did not go unnoticed. In a year already filled with royal milestones, the March 18 state banquet stood out for its elegance and emotional depth. While the primary purpose was diplomatic — strengthening ties between the UK and Nigeria — Catherine’s look added layers of beauty, history, and quiet sentiment.

As one royal style blog aptly put it, the Princess delivered yet another masterclass in storytelling through fashion. Whether through the diplomatic green or the diamond knots of the tiara, Catherine dazzled not just in appearance, but in the thoughtful messages she conveyed.

For royal enthusiasts, it was another reminder that behind the glamour lies a deep respect for tradition, family, and duty — qualities that continue to define the Princess of Wales.