With the night's revelry, fireworks and hangovers behind them, hundreds of thousands of people turned out to watch London's New Year's Day parade.
Around 10,000 performers, including cheerleaders, marching bands, musicians, clowns and vintage vehicles paraded through the city centre, watched by an estimated 500,000 people, according to organisers.
Bob Bone, the parade's executive director, said the event would boost tourism and business in the capital.
"We promised London a truly wonderful spectacle and we have delivered that," he said.
"This is a wonderful shop window for our great city. Millions of people wondering where to head on holiday this summer will get a real feel for the warmth of the welcome that they can expect to get in London."
Some of the performers flying in from the United States were delayed by storms.
At one point an antique fire engine crashed into an iconic London Routemaster bus, but nobody was injured.
The 23rd annual parade passed by some of the city's best-known landmarks, such as Trafalgar Square, Downing Street and the Houses of Parliament along its 2.2-mile (3.5-kilometre) route.
Earlier, at the stroke of midnight GMT, Big Ben, the bell inside the clock tower at the Houses of Parliament, not only rang in the New Year with its famous chimes, but also its own 150th anniversary.
Big Ben sounded for the first time on July 11, 1859.
Revellers braved freezing conditions in the city centre to see the New Year fireworks spectacular on the banks of the River Thames, which engulfed the London Eye in a blaze of colour.
An estimated 400,000 people lined the embankments to catch the 10-minute salvo, which lit up the misty night sky over the British capital.
A total of 110 people were arrested, largely for public order, assault and drunk and disorderly offences, police said.