William and Kate exchange vows

Prince William and Kate Middleton have exchanged vows at Westminster Abbey in a wedding service watched by a global audience of two billion.

PHOTOS: Kate's dress
VIDEO: Kate arrives at the Abbey
VIDEO: William arrives at the Abbey

The new Duke and Duchess of Cambridge were pronounced husband and wife in front of 1900 guests inside the abbey at 11.20am (8.20pm AEST).

The bride wore an ivory and lace wedding dress designed by Sarah Burton, creative director at the fashion house Alexander McQueen.

Earlier, Prince William arrived with best man Prince Harry at his side and faced a nervous 45-minute wait for Kate.

The groom, resplendent in a red military tunic, and his brother were greeted by cheering crowds as their chauffeur-driven Bentley drove along The Mall.

The brothers, both officers in the armed forces, looked impeccable in their uniforms as they passed thousands of well-wishers in the State Car, painted in Royal Claret Livery.

They smiled and waved to the delighted spectators as they set off from Clarence House, their London home, on William's final journey as a single man.

As the car emerged the crowd chanted: "We want Will! We want Will!"

Kirsten Oates, 35, from Boston, Massachusetts, said: "He looked so classically handsome but very happy and relaxed and very much like a future king."

As well as gaining a bride, William also gained a title today.

His grandmother the Queen gave him a traditional wedding-day dukedom so when the happy couple leave the abbey they will not just be man and wife, they will be the Duke and Duchess of Cambridge.

The last Duke of Cambridge, like Prince William, married a commoner for love. He wed the actress Sarah Louisa Fairbrother in 1847.

As the brothers passed cheering well-wishers, a short distance away in the seclusion of the exclusive Goring Hotel and surrounded by her family, Catherine was putting the finishing touches to her bridal ensemble.

The prince faces a nerve-wracking 45 minute wait at the ancient venue for his bride.

William has followed royal tradition and donned military uniform like his father the Prince of Wales and grandfather the Duke of Edinburgh before him.

The groom, an RAF search and rescue helicopter pilot, was dressed in the famous red tunic of an Irish Guards officer rather than his Air Force uniform.

He holds the honorary rank of Colonel of the Irish Guards

Captain Harry Wales, 26, newly promoted in the Household Cavalry's Blues and Royals, wore a Blues and Royals' officer's uniform in dismounted review order, with a forage cap.