Well this is a bit awkward, Prince William is double booked for Saturday 19th May.
Not only is it his brother's wedding where he'll be the best man (you know, that tiny event that billions of people will be tuning in to watch), but it's also the England Football Association final, and as president, he's expected to attend.
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Prince William has been the England Football Association (FA) president for 12 years and like any responsible royal, he takes his role seriously. In fact the Duke of Cambridge is such a footy fan that he was part of the team that pushed for this year's World Cup to be held in England, but lost out to Russia.
The wedding service at St George's Chapel starts at midday local time and the lunchtime reception hosted by the Queen is due to finish around 3.30pm. Kickoff for the match, however, isn't until 5.15pm so if everyone is happy for William to be a bit late to the evening party at Frogmore House, he could technically attend both.
It takes around an hour to drive from Windsor to Wembley Stadium, but perhaps Granny will be able to call the royal chopper to help him out.
William has always been the more responsible prince compared to former bad boy Harry, but will he go with family or royal duty? Last year, he had 190 royal engagements, and he may take some more to help dad, Prince Charles out, who made a jaw-dropping 550 appearances in 2017.
As there's been no word from Kensington Palace, we're not sure what Prince William's plans are, but stay tuned.
Newborn Prince Louis and Meghan Markle's dad Thomas Markle will be noticeably absent but the world will go into meltdown if Harry's best man is a no show!