Hundreds of thousands of people gathered on the banks of the Thames in London to watch a spectacular firework display mark the new year.
Rockets flared from the London Eye and the capital's riverside landmarks were lit up in a display which lasted 11 minutes and featured 12,500 fireworks.
Mayor Boris Johnson said: "What an amazing end to an incredible year."
About 250,000 were in the city to watch the show, which also involved clips from the 2012 Olympic Games.
Mr Johnson added: "Watched by hundreds of thousands in the capital and millions around the globe, London has proved, yet again, that it can pull off spectacular world-class events in style."
Many of the revellers had waited hours to secure the best vantage points and fortunately it was a dry and mild night.
Rob Haine, 30, a computer game programmer from Wakefield, said: "The display was mesmerising, it was a joy to witness.
"I got here at 5pm and have been standing the whole time but it was worth it. It was cool that they got the Olympics into the fireworks."
Sandro Benvenuti, 46, travelled from Italy with his wife and two daughters to see the display.
"We were waiting for six hours but it was fantastic," he said.
"We have fireworks in Italy but those were much better. They went on for longer and the design and special effects were superior."
Lynn Shepherd, 53, from North Newbald, East Yorkshire, praised the "electric atmosphere".
She said: "There's no trouble here. Everyone is having a good time and it's the perfect way to finish 2012."
The Metropolitan Police said as of 3:45 GMT, officers had made 96 arrests across the capital relating to the New Year's Eve celebrations, mainly for being drunk, public order offences and assault.
More than 3,500 police supported the organisers and stewards of the event in central London, working alongside colleagues from the British Transport Police and other emergency services to keep revellers safe.
'No major issues'
Chief Inspector John Williams said: "This year has really been one to remember and what better way to top off the success of team GB at the Olympics and Paralympics and the pageantry of the Queens Diamond Jubilee than with a world-class firework display.
"This year saw the viewing areas fill up earlier than ever before with thousands of revellers coming to see in the new year London-style.
"There were no major issues reported to police and the crowds were good natured.
"Officers continue to work through the night to facilitate the clean-up operation, ensure roads are reopened and the area returns to normality in time for the New Year's Day parade."
The Tube, DLR, tram and selected National Rail services in Greater London ran all night.
Following their work during the London 2012 Games, more than 150 Team London Ambassadors volunteered during the New Year's Eve celebrations.
They gave out maps, directed people to the viewing areas and gave guidance and advice on getting home safely.