"The duke intends to tell the Queen himself," a palace source told 'The Sunday Times'.
After his wife Kate Middleton, the Duchess of Cambridge, delivers the Queen's newest great-grandchild, the royal couple's private secretary will inform Prime Minister David Cameron and a handful of others, including the Archbishop of Canterbury.
Officials in Buckingham Palace will notify the head of each of the 54 Commonwealth countries and the First Ministers of Scotland, Wales and Northern Ireland.
Meanwhile, the Queen has put a high-speed helicopter on standby to take Prince William to Kate's bedside whenever she goes into labour. The 175mph Sikorsky S-76c chopper will rush Willam from his RAF base in Anglesey to London to be with Kate when she has the baby due to be born by next weekend.
This means the 31-year-old prince can carry on with his work as a rescue pilot until the last moment without having to worry about missing out on the birth.