Looking every inch a future Queen, Princess Kate, 41, reigned supreme in monochromatic red. The royal's cherry ensemble consisted of a billowing cape dress designed by Catherine Walker, characterised by an oversized bow adorned across the neckline.
The mother-of-three teamed her festive get-up with ruby red heels and a magnificent hat perched effortlessly on her neat, balletic chignon.
Prince William matched his wife's regal aesthetic in a suave navy suit, complementing the romantic red tones in her outfit by adding a simple silk tie in the same hue.
Princess Kate and Prince William's coordinated dressing
Fans have been quick to notice the royal power couple coordinating their outfits on a number of occasions, from their iconic festive red moment at the Princess of Wales' Together at Christmas concerts, to Prince William subtly matching his ties to Princess Kate's dresses.
HELLO! previously spoke to elationship consultant Mairead Molloy for her expert intel on the Prince and Princess of Wales' calculated colour coordination.
"Mirroring your partner's fashion choices is related to having a keen sense of empathy, and signifies a high level of happiness and content within a relationship," says Mairead. "It can also be a signifier of a special bond between a couple."
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"Harmonious dressing can be a subconscious occurrence that typically happens about six months into a relationship," explained Mariead, who credited a desire to be "closer to our partner" as a reason behind the sartorial switch.
The sartorial synergy between the royals could also signify their unity as senior royals, putting in the foundations for their future roles as King and Queen.
LISTEN: In the latest episode of HELLO!'s Right Royal Podcast, we delve into our favourite royal relationships, including the moment Prince William proposed to his then-girlfriend Kate Middleton at university.
The Prince and Princess of Wales' appearance in Westminster this morning comes before a glittering reception due to be held at Buckingham Palace on Tuesday evening.
MORE ROYALS IN RED
With a white tie dress code, royal watchers can expect the likes of Princess Kate and Queen Camilla to embrace regality in glittering gowns and tiaras from the royal collection.