A royal fan poses for a photo outside Windsor Castle one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Police stand on guard outside Windsor Castle one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Police stand on guard outside Windsor Castle one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

A royal fan camps outside Windsor Castle one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Royal fans are seen outside Windsor Castle one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Royal fans stand outside Windsor Castle one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Media gather outside Windsor Castle in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Royal fans stand in a street corner along the wedding procession route to secure their viewing spots outside Windsor Castle in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)

Souvenirs of Britain's Prince Harry and US actress Meghan Markle are on display in a shop window one day before the Royal Wedding in Windsor, Britain, on May 18, 2018. Britain's Prince Harry and US actress Meghan Markle's wedding will be held on May 19 at St George's Chapel in Windsor Castle. (Xinhua/Han Yan)