Britain cheers as Kate Middleton gives birth to future king

Britain was in full celebratory mood today as Prince William's wife Kate Middleton gave birth to a bouncing baby boy - the third in line to the throne - with hundreds thronging the street leading to the hospital hoping to catch the first glimpse of the new royal heir.

'We could not be happier,' said William, the 31-year-old Duke of Cambridge, in reference to the new prince of Cambridge, whose name is yet to be announced.

The Duchess of Cambridge, 31, gave birth to the baby boy, weighing 3.8 kilos (8 lbs 6 oz), yesterday at the private Lindo wing at St Mary's Hospital in Paddington here.

People continued to celebrate the birth of the boy even as congratulatory messages poured in from across the globe.

The fountain in Trafalgar Square was lit up with blue lighting to mark the birth of the third in line to Britain's throne and 'It's a boy' was instantly being flashed on the BT Tower in central London.

Queen Elizabeth II was the first to be informed about her newest great-grandson by phone.

Prince Charles, the grandfather of the baby, responded to news of the birth by saying he was 'enormously proud and happy' of becoming a grandparent.

'Both my wife and I are overjoyed at the arrival of my first grandchild. It is an incredibly special moment for William and Catherine and we are so thrilled for them on the birth of their baby boy,' he said.

'Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future,' Charles said.

British Prime Minister David Cameron was among the first to take to Twitter to say: 'I'm delighted for the Duke and Duchess now their son has been born. The whole country will celebrate. They'll make wonderful parents'.

US President Barack Obama said, 'Michelle and I are so pleased to congratulate the Duke and Duchess of Cambridge on the joyous occasion of the birth of their first child. We wish them all the happiness and blessings parenthood brings. The child enters the world at a time of promise and opportunity for our two nations'.

A statement issued by Kensington Palace, the Duke and Duchess' official residence, confirmed that William was present for the birth.

'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,' the statement said.