Thousands of police officers watched over New Year revellers as the night sky above London was illuminated by a spectacular fireworks display.
Crowds gathered on the banks of the Thames and in city centres across the UK to see the start of 2016.
Around 3,000 officers were deployed across central London, including firearms police, at a time of heightened global security in the wake of the Paris terror attacks.
Many braved the intermittent spells of rain awaiting a midnight display featuring around 12,000 fireworks which produced 50,000 projectiles.
The celebrations went ahead as planned, despite a similar display in Brussels being cancelled due to safety concerns.
The Edinburgh Hogmanay also saw several firework displays above the city's castle, as well as a performance from Scottish rockers Biffy Clyro.
In Dubai, the New Year celebrations were tempered by a huge blaze in one of its tallest buildings.
The arrival of the New Year was greeted by silence in Moscow - the fireworks display was five minutes late.
The Met confirmed New Year's Eve was one of two events - along with Notting Hill Carnival - in which there was no holiday entitlement, meaning all available staff were called upon.
The force said it had worked closely with the mayor's office, British Transport Police (BTP), Westminster City Council and others to ensure the event ran smoothly.
The mayor's fireworks display was ticketed for the second year and was sold out.
Metropolitan Police spokeswoman Superintendent Jo Edwards said the extra officers were for reassurance.
She said: "We want people to be reassured, not frightened by the number of police officers they may see."
Today, more than 8,500 performers representing 20 countries will take part in the annual New Year's Day parade through London.
The event, which includes marching bands, cheerleaders, clowns and acrobats, kicks off in Piccadilly and finishes in Parliament Square, taking in Lower Regent Street, Pall Mall, Trafalgar Square and Whitehall.