But don't get too excited. According to E! News, the queen spent almost an hour at the event, so it's highly possible her sudden departure was merely a way to beat the crowd.
Since Middleton's due date was expected to be July 11, the royal baby is expected at any time.
As for the queen, she hopes it's sooner than later.
When asked by a schoolgirl at a public event whether she was hoping for a boy or a girl, the queen said, "I don't think I mind. I would very much like it to arrive. I'm going on holiday."