He did, and so did his wife, as they both delivered a flawless performance during the wedding ceremony.
There were 1,900 guests in Westminster Abbey, hundreds of thousands of well-wishers lining the streets of London, and as many as two billion people watching around the world.
And the couple got their marriage off to a perfect start, both beaming with pleasure.
On an impromptu walkabout on Thursday night William, told well-wishers “All I’ve got to do is get the lines right.” He need not have worried.
Both he and Kate, now the Duchess of Cambridge, spoke confidently as the Archbishop of Canterbury, Dr Rowan Williams, solemnised their marriage.
Before the ceremony William and Prince Harry had the demeanour of any other groom and best man.
Both checked their hair, patting it down after removing their hats as they entered the abbey.
William chatted with guests, smiling and looking relaxed, while Harry appeared the more nervous of the two.
The bride-to-be arrived at Westminster Abbey at exactly 11am. She was all smiles as she walked up the aisle accompanied by her father, Michael.
As she approached the front of the church, Harry looked back, cracked a broad smile and said a few words to his brother.
William faced forward until Kate arrived.
The couple looked lovingly at each other as they exchanged a few words, William looking down to admire the length of Kate’s dramatic dress.
The Archbishop asked William: “Wilt thou love her, comfort her, honour and keep her, in sickness and in health; and, forsaking all other, keep thee only unto her, so long as ye both shall live?”
William’s voice crackled slightly as he said: “I will.”
As Kate said “I will” to the same vows there was a loud cheer from the crowd outside.
Like Diana, Princess of Wales, Kate did not promise to obey her husband.
William spoke steadily and confidently as he repeated the words after the Archbishop, saying: “I, William Arthur Philip Louis, take thee, Catherine Elizabeth to my wedded wife, to have and to hold from this day forward, for better, for worse: for richer, for poorer; in sickness and in health; to love and to cherish, till death us do part, according to God’s holy law; and thereto I give thee my troth.”
Kate took William by his right hand to repeat her vows, which she delivered without fault and which received another cheer from the crowd outside.
There was a nervous moment when William tried to put the ring on the fourth finger of Kate’s left hand.
The ring was stuck on the knuckle for a few seconds but then slipped on.
There was more cheering from the crowd outside as the Archbishop pronounced them man and wife.
In 1981 Diana’s nerves showed briefly when she called her new husband Philip Charles Arthur George rather than Charles Philip.
The Prince of Wales also slightly muddled his vows, referring to “thy goods” rather than “my worldly goods”.
“You look beautiful.” — What Prince William seemed to be whispering to Kate at the altar
“We’re supposed to have just a small family affair.” — William jokes at the altar with the bride’s father Michael Middleton
“Those people who were so recently sneering at her background, and nicknaming her ‘Waity Katie’, will soon be lost in admiration of her poise and professionalism.” — Historian Andrew Roberts
“Checkmate Kate — you’ve taken the King!” — Words on a banner among the cheering crowds
“We’ve got Middleton’s Mushy peas, Kate’s Cod, Buck House Burgers. I drew the line at getting some skate in.” — Peter Beedle, Kate’s cousin describes the royal menu at his fish and chip shop in Durham
“She is so stunningly beautiful, it’s so regal, it’s such understatement that I think it’s just perfection. Everybody is starstruck with her gown.” — Harold Tillman, chairman of the British Fashion Council
“Kate wearing her hair as she has is the death of the straightening iron. It’s all about a girl’s best friend — the heated roller.” — Celebrity hairdresser Andrew Barton
“I pray that everyone present and the many millions watching this ceremony and sharing in your joy today will do everything in their power to support and uphold you in your new life.” — Bishop of London Dr Richard Chartres in his address in Westminster Abbey
“Beautiful service. Very moving. On a double-decker bus from the Abbey to the Palace. Had to show a bank statement to security to get on.” – Broadcaster and adventurer Ben Fogle tweeted
“We’re quite a reserved lot, the British, but when we go for it, we really go for it.” – Prime Minister David Cameron
“Even so long after ‘Charles ‘n’ Diana’ was exposed as a sham act, Britain is still in thrall to a vulgar fascination with bloodlines and a barkingly insane notion of monarchy.” — Writer Will Self
“Poor Posh — she is trying so hard not to smile because she doesn’t like her face when she does, but she desperately wants to.” — Sports broadcaster Clare Balding on Victoria Beckham.