There's a special detail in this never-seen-before Royal photo of William and Kate

Kate Middleton and Prince William have shared a never-seen-before photograph to mark their 13th wedding anniversary and it reveals a special detail we missed back in 2011. 

The Prince and Princess of Wales released the black and white portrait, which was photographed by British photographer Millie Pilkington, on their Instagram page alongside the simple caption: "13 years ago today!"

The shot shows the couple beaming at the camera, both looking immaculate. Princess Catherine is pictured in her iconic Sarah Burton for Alexander McQueen gown wearing the stunning Cartier Halo Tiara, while William is dapper in full military dress, wearing the black frock coat uniform of the Blues and Royals. 

But eagle-eyed royal fans will notice there's a sartorial significance to this image. On closer inspection, Prince William is actually wearing a completely different outfit to the one he walked down the aisle in. 

Walking down the aisle in Westminster Abbey, William wore the scarlet tunic of the Irish Guards. The Prince of Wales was the Colonel in Chief of the regiment at the time, a post that his wife Catherine took over later in 2022. 

In his revealing memoir Spare, Prince Harry delves into more detail on William's outfit switch-up, claiming that his brother was "frustrated" over his lack of control of his outfit. Harry wrote in the book, which was released in 2022: "He’d asked Granny if he could wear his Household Calvary kit, and she’d turned him down. As the heir, he must wear the Number One Ceremonial, she decreed," before going on to say that "Willy" felt "frustrated" over the instruction from his grandmother and was "glum at having so little say in what he wore to get married". 

Royal watchers will note that William changed into his second ensemble, the black frock coat uniform of the Blues and Royals, for the couple's evening bash. The evening festivities also saw Catherine do a quick outfit change. The Princess of Wales changed into a second Burton for Alexander McQueen dress, with a fitted bodice and full skirt, tied together with a bejewelled section around the waist and finished off with a white textured bolero. 

Photographer Pilkington also shared the photo with a sweet message to the couple, writing: "Wishing the @princeandprincessofwales the very happiest wedding anniversary. Can’t believe it is 13 years ago almost to the hour, that I took this portrait. So excited and honoured that they should wish to share it."

Pilkington joined the hundreds of royal fans wishing William and Catherine a happy anniversary. "Happy anniversary William and Catherine. The beginning of one of the best partnerships the Royal family has ever seen!" wrote one fan. While another commented: "Happy anniversary! Praying for Kate’s health and full recovery every night. She is such an inspiration of elegance, beauty, grace and discretion for me since 2010. Sending your beautiful family lots of love."