Meghan Markle leaves the Cliveden House Hotel, for her wedding at St George's Chapel at Windsor Castle to Prince Harry. Picture: Darren Staples/Reuters

Windsor — American actress Meghan Markle arrived at Windsor Castle for her wedding to Prince Harry, wearing a white veil and diamond tiara for a glittering union of British royalty and Hollywood glamour that will be watched by millions around the world.

Prince Harry, dressed in a military frock coat uniform, and his brother, best man Prince William, had already entered the 15th-century St George's Chapel, which was adorned in white roses, favorite flowers of their late mother Princess Diana.

After entering the chapel unescorted, Markle will make her way to the organ screen halfway down the church, from where heir-to-the-throne Prince Charles will walk her down the aisle to his son, Prince Harry.

Tens of thousands of fans lined the route Markle took toward the castle, waving British flags and cheering as the Rolls-Royce limousine drove past with Markle and her mother, Doria Ragland, 61.

"This is a moment when we can all celebrate the rebirth of the royal family," said Kenny McKinlay, 60, who had come down from Scotland for the wedding. "It's a time when all the nation can come together rather than being divided. It's a day when you can be proud to be British."

The couple, who met on a blind date in 2016 and fell in love in a tent under the stars in Botswana, will tie the knot at the 15th-century St George's Chapel, in a castle that has been home to 39 English monarchs since 1066.