Prince William's newborn son is sleeping ''reasonably well.''

The 35-year-old royal welcomed his third child into the world with his wife Duchess Catherine on Monday (23.04.18) and, although it's still early days, the tiny tot is ''behaving himself'' thus far and isn't having his parents up too much in the night.

William joined his brother Prince Harry and his fiancee Meghan Markle at Westminster Abbey to mark Anzac Day on Wednesday (25.04.18) and said when asked how the duchess and baby were doing: ''They're very well thanks.

''They are in good form, luckily. Sleeping's going reasonably well so far, so he's behaving himself which is good news.''

The couple - who also have four-year-old son Prince George and two-year-old daughter Princess Charlotte together - are yet to announce the name of their baby, but William did joke that ''Jerry's a strong name'' after he met the New Zealand High Commissioner to the UK, Sir Jerry Mateparae at the beginning of the service.

The Dean of Westminster suggested: ''Jerry would like it to be Jerry.''

To which the prince replied: ''Jerry's a strong name.''

The duchess, 36, was taken into St. Mary's hospital in Paddington, London, in the early hours of Monday morning in labour and by 11am the prince had been born.

Shortly after the baby's birth, Kensington Palace confirmed in a statement: ''Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 1101hrs.

''The baby weighs 8lbs 7oz.

''The Duke of Cambridge was present for the birth.

''Her Royal Highness and her child are both doing well.''

Both William and Catherine's family are ''delighted'' with the new addition.

The statement concluded: ''The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news.''