Stepping out of the luxurious car, the pretty Canadian was greeted by the cheers of around 200 onlookers who had braved the inclement weather.
Leading the arrivals from the royal family were Princess Anne and her husband, Captain Tim Laurence. They were joined by the groom's father, Mark Phillips, and his wife, Sandy Pflueger. The royals were soon followed by Autumn's mum, Kitty, along with the groom's aunt and uncle, the Duchess of Cornwall and Prince Charles, and his cousin, Prince Harry.
Accompanying the Prince of Wales' younger son were his girlfriend, Chelsy Davy, 22, and Prince Williams' love Kate Middleton. William himself was unable to be at the wedding.
Last to enter the impressive 15th century St George's Chapel were Peter's proud grandparents, Queen Elizabeth and Prince Philip. The Queen wore a long silver and bronze coat with matching feather fascinator for the wedding of her eldest grandchild.
The 300 guests â€“ 70 of whom had travelled from the bride's native Canada â€“ sang hymns including Now Thank We All Our God. The readings were performed by Autumn's half-brother, Patrick Kelly, and Princess Eugenie, who recited Shakespeare's Sonnet 116.
After the moving ceremony, the newlyweds - both wearing wide smiles - were whisked away in a romantic horse and carriage to begin their celebrations.