Royals and other guests arrive at the church.
Homeless girl's royal wedding invite
Prince William invites girl who used to sleep rough to his nuptials
The 20-year-old girl named Shozna will be one of the guests at the wedding of the year.
Shozna became homeless after suffering a stroke in 2009 and was helped back on her feet by Centrepoint, a charity Will's mother Princess Diana used to do fundraising work for.
Prince William met the girl at a Centrepoint gala last year and was moved by her story.
Shozna, who will wear a dress given to her by bridal wear designer Raishma Islam, said of the invitation "I'm so very excited. Kate seems born to be a princess and I think she'll look traditional and elegant. I can't believe the Beckhams , Elton John and his husband, Prince Harry and all the little bridesmaids will be there"
She also added "Congratulations. Thank you for inviting me and thank you for making people feel like they are part of the world instead of being alone".
A spokesperson for St James's Palace confirmed the invitation.
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