While the official statement simply cited "a scheduling conflict" as the reason behind the altered performance schedule, there's speculation that he will be busy that weekend celebrating the union of Prince Harry and Markle. Once inside the castle, they will observe the firing of the One O'Clock Gun - a tradition that started in 1861.
In addition to getting familiar with the UK, Meghan is also preparing for her big day.
Their first stop was to Edinburgh castle, where the couple was met by hordes of fans.
However, Cpl Cruachan IV has form when it comes to nibbling royals - in July 2017 he took a swipe at a bunch of flowers held by The Queen as she visited Stirling Castle.
After visiting the castle, Harry and Meghan will go to Edinburgh's New Town to visit Social Bite, a café that distributes food and hot drinks to the homeless. "My prediction is that Meghan is going to be our new Diana".
When a woman in the crowd wished her good weather for the wedding, Meghan joked: "Being in the United Kingdom, all I do is talk about the weather now". "A wee touch of Meghan adds a bit of sparkle".
Prince William and Prince Harry - who did not accompany Markle on her trips - have both visited the Al Manaar mosque since.