Prince Harry has said his brother would love to have a low-key wedding, were it not for his position.
"If he had it his way, he would have a normal wedding with just his close friends," he told the BBC.
And whilst in many ways that may not be possible, Harry plans to fulfil his role as best man in the traditional way.
He will give Prince William, 28, a roasting during his speech.
Along with a couple of the groom's friends, Harry intends to "dig him in the ribs and embarrass him. Make him lose some hair."
"The speech will be like any best man's speech, between the three of us we will make sure people know the good times and bad times since he was a nipper."
But the 26-year-old also acknowledged that the speech will have to be "selective" due to his grandmother, the Queen's, presence.