The Princess of Wales broke with royal tradition during the first Easter Sunday service of King Charles' reign yesterday.
Kate wore a marine blue Catherine Walker coat and matching pill-box hat by Lock & Co as she attended St George's Chapel at Windsor with Prince William and their three children.
She matched the outfit with a deep red nail polish, despite usually opting for lighter tones or no varnish at all.
It's long been rumoured that royal ladies are not allowed to wear brightly coloured nail polish, with clear varnish, nude or light pink tones said to be the only acceptable shades.
The late Queen certainly abided by this "rule" as she was only ever seen sporting nude or lightly coloured nails with Essie's shade 'Ballet Slippers' a personal favourite.
The unofficial rule was thought to be particularly implemented during the late Queen's reign. However, it appears the rule may not exist at all after Kate's appearance on Sunday.
It comes after Sophie, the Countess of Wessex, was also seen wearing a deep red nail polish during a four-day tour of New York last month.
Yesterday's service saw the royal family out in force in the grounds of the castle, enjoying the bright spring sunshine before the morning service.
Charles and Camilla wore matching royal blue outfits, with the King in a suit and the Queen Consort wearing a coat dress by Anna Valentine with a Philip Treacy hat.
They left the service separately, with Camilla stopping to receive a bouquet from Harriet, 10.
Camilla waved to members of the public and wished them a "Happy Easter", before getting into a waiting car.
Charles also greeted the crowd, receiving a round of applause as he left a few minutes later.
William and Prince George wore matching navy suits at the service yesterday, while Princess Charlotte wore a blue polka-dot dress.
Prince Louis, attending the service for the first time, wore a suit jacket and light blue shorts.
Kate stopped after the service to receive a posy from eight-year-old Samuel. She smiled at him and shook his hand before before waving to the public as she left.
They were joined at the service by the Princess Royal and the Duke of York. Andrew wished the public a "Happy Easter" as he left.
The Duke and Duchess of Edinburgh also attended with their son James, the Earl of Wessex.
Princess Beatrice and her husband, Eduardo Mapelli Mozzi, also attended the service, as did her sister Princess Eugenie and her husband, Jack Brooksbank, and Zara and Mike Tindall and their two daughters, Mia and Lena.
It was likely to have been a moving moment for the royal family, with the 15th century chapel being the late Queen's final resting place and the Easter Sunday service the first to take place since her death.
Elizabeth II is buried in the church's tiny King George VI Memorial Chapel, alongside Prince Philip, the late Duke of Edinburgh, and her parents, George VI and the Queen Mother, with their four names inscribed on a new black stone slab set in the floor.
Charles, as monarch, has succeeded his mother to become the Supreme Governor of the Church of England.
In less than a month's time, he will be crowned alongside Camilla in a religious service in Westminster Abbey.
