London Mayor Sadiq Khan has moved to reassure New Year revellers amid a massive security operation surrounding the capital’s celebrations.
The extra security measures are in place due to fears of a lorry attack similar to that seen at a Christmas market in Berlin earlier this month.
As revellers started flocking to the banks of the River Thames for the capital’s sold-out fireworks display, a huge police presence was on the streets.
Armed police will be deployed on London Underground trains for the first time on New Year’s Eve, and a record number of concrete bollards have been placed at junctions in central London to keep vehicles away from the crowds.
British Transport Police said officers would work extended hours on New Year’s Eve for the second year in a row.
Mr Khan said the fireworks would be “the best any city in the world is having tonight”, adding he had seen “no evidence” that Londoners and visitors to the city had been discouraged from celebrating the start of 2017 due to recent terror attacks.
:: New Year celebrations around the world
He said the display would pay tribute to some of the artists who died in 2016.
Mr Khan told Sky News: “Our police and security services do an amazing job learning the lessons from some horrific incidents in other cities around the world – Berlin recently, Nice earlier this year, Paris last year.
“We adapt to make sure we preserve our way of life but keep our citizens and those visiting safe.
“We will have more than 3,000 visible police officers on the streets of London and at stations, but also we don’t want to stop people having a good time.
“We’ve got to make sure we don’t allow terrorist or people who want to destroy our way of life to stop us enjoying what’s going to be a great night.”
And forces across the country are also on alert.
West Midlands Police said: “While the security status remains at severe we have further resources in place should they be needed.”
In Scotland, some 80,000 people are expected to pack into Edinburgh city centre to celebrate Hogmanay.
Police Scotland said it had “reviewed” safety plans following the recent truck attack on a Christmas market in Berlin.
Chief Superintendent Kenny MacDonald said: “We are absolutely confident that the plans that we have in place are proportionate and appropriate, and we will make sure that we deliver a safe event.”
The celebrations in Hull will focus on New Year’s Day when the city kicks off its tenure as City of Culture with a huge fireworks display it says will rival London’s New Year’s Eve party.
UK authorities say they are not responding to any specific intelligence of a threat, but are taking precautions after recent events in Europe.
In July, Mohamed Lahouaiej Bouhlel killed 86 people when he drove a 19-tonne lorry into crowds on Nice’s seafront promenade.
Earlier this month, Anis Amri killed 12 people when he drove a hijacked lorry into a Berlin Christmas market.
Metropolitan Police Commissioner Sir Bernard Hogan-Howe told Sky News: “One of the things we’ve had to consider are the attacks in Nice and Berlin which used vehicles, so we’ve done our best to anticipate that and put measures in place that will keep people safe.
“It’s impossible to guarantee everything and I think everybody understands that.
“But we can take reasonable measures and I’m sure that’s what we’ve done tonight.
“I just hope we have a great night in London – that’s what usually happens every year, no reason to suspect that it won’t, but of course we’d be professionally negligent if we didn’t take reasonable steps – and that’s what we’ve done.”