Prince William was drunk on rum to calm his nerves just hours before his wedding, according to Prince Harry ’s bombshell book.
Harry claimed he told William that he "smelled of alcohol", and even offered him mints.
Prince William and Kate tied the knot at Westminster Abbey on April 29 of 2011, after 10 years of on/off dating, with Prince Harry standing by his brother's side during the lavish ceremony.
Harry's autobiography, Spare, isn't set to be released in the UK until January 10, but excerpts from the book were leaked ahead of its release after it was accidentally sold early in Spain.
In one such excerpt, Harry wrote that in the build up to his big brother's wedding, Prince William "begged" him to accompany him while he went down to greet people camping out on the Mall; the avenue that goes from Buckingham Palace to Trafalgar Square.
Harry wrote that "Willy, already tipsy from the rum, shouted: 'Let's go down and see them!'."
According to a translation of the leaked excerpts, William was told by the security team that the visit was "strongly discouraged" but he told them he needed to "see the people".
Describing how the pair travelled together to the Mall ahead of the big day in 2011, Harry wrote that they went out into the street and shook hands with people, who wished "Willy" well, and told him that they loved him and Kate.
But in Harry's account of the day, he said it was "impossible not to hear the echo of the worst" day back in August 1997, after the death of their mother Princess Diana.
Harry next wrote of how the pair were "physically and emotionally exhausted", and it seemed that his brother had not rested before he went to pick him up the next morning.
"I was stunned when I went to pick him up in the morning and saw his haggard face and red eyes; It seemed that he had not slept at all," Harry wrote.
When he asked William if everything was fine, his brother said yes, Harry wrote, before going to on to claim this seemed not to be the case.
When the car began to move, Harry wrote, he broke the silence to tell his brother he "smelled like alcohol" - in what he supposed was the "aftermath of the rum from the night before".
He described how he opened the window a little, covered his nose and offered William mints "by way of mockery".
In the same excerpt, Harry wrote of how William had been unhappy about not having a say over his wedding attire.
While he had wanted to wear the cavalry uniform and frock coat of the Royal Guards, he was made to wear the "the bright red uniform of the Irish Guards," Harry recounted.
In another section of the book, the prince details how he was suffering from a frostbitten penis during William and Kate's wedding.
Harry recounts his painful experience with frostbite — which he said affected his ears, cheeks and 'todger' — following a 200-mile Arctic charity walk ahead of William's big day.
The prince's Walking with the Wounded expedition saw him embark on a brutal journey to the North Pole alongside four ex-servicemen who were injured in Afghanistan.
The team raised £2 million for the Walking with the Wounded charity during the 13-day trek, but the journey didn't come without its downfalls.
In his book, Harry reveals that while standing by Prince William's side during his wedding on April 29, 2011, he was actually still recovering from the icy injuries, Page Six reports.
He recalled that his father, King Charles, was "interested" and "sympathetic" about his "frost nipped" ears and cheeks.
But the injuries to his face were the least of his worries, as he wrote: “While the ears and cheeks were already healing, the todger wasn’t. It was becoming more of an issue by the day".
Harry then wrote that he eventually went to the doctor after using Elizabeth Arden cream.
