Prince William's close friend, British oarsman Oliver Hicks, has welcomed the "great and happy news" of the arrival of his son.
A statement said: 'What great and happy news to hear the baby has arrived safe and well and Kate's well too. My thoughts are with them all on this momentous day.
"I wish them all good fortune for the future. I'm delighted to be back from the sea to hear the news!."
The Queen has returned to Buckingham Palace as the world waits for the birth of the Duke and Duchess of Cambridge's first child.
A look at how the impending arrival of the Duke and Duchess of Cambridge's baby is being covered around the world.
The front page of the Guardian website features a "Republican" switch which turns off all royal baby coverage.
Australia's Courier-Mail website leads with the headline "Royal baby is on the way".
Prince Charles looked perplexed when a bystander shouted "congratulations" to him during a visit to York Minster.
Charles appeared to say "Who? Me?" before chuckling as the woman explained the greetings were for the "imminent arrival".
As the Prince walked over to her, he joked, "Do you know something I don't?"
Prince Charles was given a gift for the upcoming addition to the royal family during his visit to York.
As he accepted the gift, Charles said the baby "hasn't quite appeared yet".
Alex Dickinson said her son Freddie "thinks [the baby] is going to appear in six hours time", to which the Prince replied, "You might be right".
- The baby will be the Duke and Duchess of Cambridge's first child
- William and Kate will have been married for two years when the baby is born
- He or she will be third in line to the throne and the Queen's third great-grandchild
- Prince Harry will be bumped down to fourth in line to the throne
- The baby will one day be head of state of 16 countries
- William and Kate will both be 31 when the baby is born
- Royal births are celebrated with a 41-gun salute
- If the baby follows the Prince of Wales and William on to the throne, he or she will be the 43rd monarch since William the Conqueror in 1066
- It costs £6,265 for a one night stay and delivery package at the private Lindo wing including a suite of two rooms, but this excludes consultant's fees
- The Duchy of Cornwall landed estate - which will privately fund the baby's future as an heir apparent - has a yearly income of £18.3 million.
The Lindo Wing at St Mary's Hospital in Paddington, London, where the Duchess of Cambridge is due to give birth, is an exclusive private facility offering "bespoke care packages".
Fully refurbished in 2012, the wing describes itself as having offered "leading private obstetric and neonatal care for 60 years".
It has private en suite rooms designed to provide "comfort and privacy". Deluxe rooms and suites are also available.
A normal delivery package including a one-night stay costs £4,965, with an extra night in a deluxe room costing £1,050, plus consultant's fees which can come to around £6,000, depending on the care required, meaning a two-night stay can cost more than £12,000.
A suite of two rooms, with one used as a living room, costs £6,265 for a one-night stay with normal delivery and £2,200 for each extra night, meaning a two-night stay, with consultant fees of an estimated £6,000, would cost around £14,465.
Each room has a satellite TV with major international channels, a radio, a safe, a bedside phone and a fridge.
The expectant mother and her visitors can access the internet via wifi and there is a choice of a daily newspaper delivered to the room each morning. Toiletries are also provided.
All meals are freshly prepared in a dedicated kitchen and tea and coffee is provided for mothers and guests throughout the day.
The wing also offers a "comprehensive wine list should you wish to enjoy a glass of Champagne and toast your baby's arrival".