The Duchess of Cambridge has given birth to a second baby son.

For the first time ever, Kensington Palace announced the news to the world on its Twitter account first, before the traditional note was pinned to the gates of Buckingham Palace.

The tweet read: "Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 11.01 hours.

The baby weighs 8lbs 7oz.

"The Duke of Cambridge was present for the birth. Her Royal Highness and her child are both doing well."

The child, who has yet to be named officially, will be fifth in line to the throne, after his grandfather Prince Charles, father Prince William and elder siblings George and Charlotte. The new son's birth pushes Prince Harry down to sixth in line.

William and Kate chose not to find out whether they were having a girl or a boy at their scan.

While they are likely to have privately chosen a name for their new son, no name is expected to be revealed to the general public until later this evening or tomorrow at the very earliest.

Favourite names at the bookmakers include Arthur and Albert, with Frederick, James and Philip also on the shortlist.

However, despite the baby being born on St George's Day, the name George is out, having already been chosen by the couple for their first son.

News that Kate had travelled by car to the Lindo wing of St Mary's Hospital in Paddington, in the "early stages of labour", was revealed by Kensington Palace Twitter account first thing this morning.