A record 6,000 police officers will be on duty here today and other forces across the UK will also deploy extra officers at New Year celebrations.
"The public will probably see more police officers on the streets as part of our policing plan. They may see more visible firearms officers as well. But it's all part of the aim of our plan, which is to provide safety and security for those coming into London, and also to reassure not frighten people," a Met Police spokesperson said.
It is for the first time that the armed officers' leaves have been cancelled due to New Year, although such steps have been taken for key events previously such as the London 2012 Olympics, according to the Telegraph.
London Mayor Boris Johnson stressed that it will be "business as usual" in the city, which is flooded by locals and tourists to witness the fireworks on the banks of the river Thames.
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"From our fantastic fireworks on the banks of the Thames to thousands of events in pubs, clubs and restaurants across the city I'd urge Londoners and visitors alike to get out there and soak up the best we have to offer. As with any other major event in the capital our policing response will be appropriate, but I'd stress we've seen nothing to suggest a specific threat to London," he said.
The city's extra high terror alert for tonight comes as Belgium cancelled its annual fireworks and festivities in the capital Brussels which witnessed 10,000 people at last year's festivities. Last month, Brussels was placed under a four-day lockdown closing universities, schools and the metro system, amid fears of a Paris-style attack.
The shootings and bombings in the French capital left 130 people dead and hundreds wounded. Belgium and Brussels have been central to investigations into the Paris attacks, which are thought to have been masterminded by Belgian national Abdelhamid Abaaoud.