Many in the British press have predicted that the first child of the prince and the Duchess of Cambridge, formerly known as Kate Middleton, is expected to arrive on Sunday. Dozens of bleary-eyed photographers and cameramen have been standing guard around the clock on royal baby watch outside St. Mary's Hospital in London.
But the prince was enjoying a game of polo against his brother Prince Harry at a charity event at Cirencester Park Polo Club, almost 100 miles (161 kilometers) west of the capital, on Sunday.
According to bookmaker William Hill, most people are betting money on a royal birth Sunday, Monday or Tuesday.
Officials have said that the baby is due around mid-July, but have not released a due date. The birth, when it does come, will be announced by a bulletin posted on a wooden easel placed outside Buckingham Palace.
It's a time-honored royal tradition - the birth of William's father, Prince Charles, was announced the same way in 1948. This time, however, officials have adapted to modern times by adding a simultaneous announcement on Twitter, so that millions around the world can get the news within seconds.
Rupert Adams, spokesman for William Hill, said that the most fervent betting has been on the name of the baby. Alexandra, Charlotte, Elizabeth and George are among the top contenders so far, he said.