The Duke and Duchess of Cambridge tied the knot in a beautiful ceremony at Westminster Abbey in front of millions of people.
Every detail was meticulously planned months before their big day in 2011, from the guest list to the venue and the menu.
However, a leaked secret threatened to ruin the big day.
Like many brides, the then Kate Middleton wanted to keep details of her wedding dress a secret until she walked down the aisle.
But despite doing everything in her power to keep the designer a secret, news got out - the Mirror UK reports.
The secret designer was leaked and revealed to be Alexander McQueen's Sarah Burton.
Speaking on Channel 5 documentary Secrets of the Royal Dressmakers, royal expert Katie Nicholl discussed how much this upset the future Duchess of Cambridge.
She said: "Behind the scenes, I think that caused tears at the Palace because Kate had done everything she could to keep the wedding dress a secret."
Almost two months before the Duke and Duchess were meant to marry, The Sunday Times revealed Sarah was the designer.
At the time, the publication reported: "She was selected by Middleton, who is making increasing efforts to develop her own style, on grounds of her quirky elegance, discretion and low profile.
"A fashion source said that the dress will be a combination of Middleton's own design ideas and Burton's deep knowledge and understanding of high fashion.
"Middleton had hoped to keep Burton's name quiet until the wedding."
Burton denied any involvement until she was officially announced as the designer on the wedding day, where she was present to help style Kate's dress.
But the leak didn't appear to dampen Kate's mood on the day as she couldn't have looked happier to marry her prince.
Wedding dress designer Caroline Castigliano says the big reveal was still special, even though the designer had been leaked as no one had actually seen it before the day.
She said: "Everybody loved Kate’s dress. That excitement when she stepped out, it was just ‘wow’.
"Incredible. She looked sensational. Even now it gives me butterflies."
Sarah used traditional Carrickmacross craftsmanship to make the dress, a technique dating back to the 1800s, to represent 'something old'.
Individual lace roses, thistles, daffodils and shamrocks were attached by hand to the ivory silk tulle, and the skirt was crafted with white satin gazar arches and pleats to echo an opening flower.
