William, who is destined to become king after his father Prince Charles, and Kate met at St. Andrews University in Scotland. They married at Westminster Abbey in London on April 29, 2011.
The birth will be announced in both traditional and modern fashion.
A proclamation will be placed on an easel in the grounds of Buckingham Palace for the public to see. At the same time, Kensington Palace will release the news on its Twitter feed.
The birth will be celebrated with a 41-gun salute in London’s Hyde Park — the standard 21 rounds with an extra 20 because it is a royal park.
The Tower of London will fire 62 rounds: 21, plus 20 because it is a royal palace, and a further 21 because it is in the historic City of London.