King of pop Robbie Williams turned down an invitation to join the fun. He wasn't free on that date.
But the other stars on the guest list make up for his absence!
The concerts are free, but you'll have to apply for one of the 12,000 tickets.
Royal official Sir Michael Peat explained: "She would have liked to ask all the people in the country to come, but they wouldn't fit in!"
You won't miss out
So organisers will decide who gets a ticket to make sure people from all over the country get a fair chance.