Even his then-girlfriend of several years, Kate Middleton, had been invited to the young prince’s passing-out parade on December 15, 2006, with her parents, Michael and Carole Middleton.
Kate was seated along the front row, and, according to a lip reader used by ITV News, she later declared: ‘I love the uniform, it’s so sexy.’
The 24-year-old sat next to William’s best friend, Thomas van Straubenzee, and his godfathers, King Constantine II of Greece and Lord Romsey.
It marked Kate’s first official appearance with the Royal Family.
She had recently graduated from the University of St Andrews and was working as an accessory buyer for High-Street store Jigsaw.
‘Her arrival completely overshadowed that of Prince Charles, the Duchess of Cornwall and the Queen,’ the Daily Mail’s Rebecca English wrote at the time.
Royal author Tina Brown described Kate’s attendance as a ‘thrilling public show of commitment’ in her book, The Palace Papers.
The future princess wore a scarlet coat and a black hat by Philip Treacy, ‘adorned by what looked like enormous heart-shaped broadcast antennae,’ Ms Brown wrote.
She accessorised the outfit with a pair of black leather gloves by the Serbian designer Evica Milovanov Penezić which featured an intricate cut-out detailing.
Kate’s mother ‘made the rare gaffe of chewing nicotine gum throughout, and was hazed for it in the coverage’, the royal author added.
William stood at the end of his platoon and carried the Queen’s banner during the parade.
He wore a blue uniform, hat and white gloves with a scarlet-coloured sash.
The 24-year-old was one of 233 cadets who were commissioned at the Royal Military Academy.
As his grandmother, Queen Elizabeth, inspected the soldiers she paused next to William to whisper hello. The prince reportedly smiled back.
He was wearing a Jubilee medal that the Queen gave to him to mark her 50 years on the throne.
William became a Second Lieutenant and no longer had to salute his younger brother, Prince Harry, who had been commissioned earlier that year in April.
Both princes joined the Blues and Royals regiment.
Harry and his fellow soldiers had also been inspected by the Queen, who was commander-in-chief, and shared a sweet interaction with her.
When she approached Harry, the late monarch reportedly said: ‘Here’s a face I recognise.’
Harry, holding a sword, is said to have beamed back at his grandmother.
After William’s ceremony, Kate and her parents enjoyed lunch with the Royal Family for the first time.
The prince reportedly fit in with his fellow cadets just like any ordinary person and was described as ‘a normal guy’ on the day of his passing-out parade.
Angela Laycock, who was a Junior Under Officer in William’s platoon at the time, previously said: ‘I’ve not really noticed anything different to be honest. The first loaded march we had a bit of a detour to avoid some photographers.
‘He’s just a normal guy that gets stuck in like everybody else.
‘The only difference is that sometimes we’ll see his name in the paper and you didn’t notice he’d been off that evening doing a charity do. I don’t know how he manages to fit that in.’
Almost two decades later, Kate wore the same hat she donned at William’s passing-out parade to last year’s Remembrance Sunday service.
Now married to William, Kate chose the timelessly elegant accessory again in a sweet nod to her husband’s military service as she watched him lay a wreath at the Cenotaph.
