Congratulatory messages are flooding in from around the world to mark the birth of the Duke and Duchess of Cambridge’s son, the third in line to the throne.

Prince William said the couple “could not be happier” following the birth of the boy, who weighed 8lb 6oz and is yet to be named, at 16:24 BST on Monday.

BBC royal correspondent Nicholas Witchell said the expectation is that they will leave hospital on Tuesday.

The birth will also be marked later with a series of gun salutes.

The duke was at the private Lindo Wing of St Mary’s Hospital, west London, for the birth – and stayed with Catherine and the baby overnight.

Leaving hospital

The couple are expected to talk to their medical team before they make any decision to go home.

BBC royal correspondent Peter Hunt said that in the meantime it was unlikely the Queen would visit her great-grandchild in hospital, adding “she can of course see him privately once he leaves”.

At Buckingham Palace, royal watchers and tourists are queuing in the rain to catch a glimpse of a bulletin announcing news of the birth, which is being displayed on an easel.

The notice is to be on show for 24 hours, which means it is likely to be removed just after 20:00.

Guardsmen outside the palace brought a celebratory feel to the proceedings ahead of the Changing of the Guard, playing “Congratulations” to the crowd.