There will be an increased presence of armed police officers on London's streets for New Year's Eve, a police official said on Tuesday (29 December). Britain is on its second-highest alert level of "severe", meaning an attack by militants is considered highly likely. Other European capitals are on similar alert levels.

"We will have about 3,000 officers in central London on Thursday night and the public will probably see an increased number of police officers, and that will include firearms officers, include city of London officers and British Transport Police have their own policing plan at transport hubs which will also include firearms officers," said Metropolitan Police Superintendent Jo Edwards.

"So the aim of the plan is to provide a strong, proportionate response and to reassure people so they can come into London and enjoy the festivities."

The New Year is welcomed in on the streets of central London by the annual Mayor of London's firework display on the stroke of midnight. The event is popular and attracts thousands of revellers to the heart of England's capital.

"I must stress that there's nothing specific directed at the New Year's Eve celebrations in London. We're policing at the general threat level of severe in the UK, which is what we have been policing to for some time," Edwards said.

"There will be increased search regime so we would ask people who have tickets for the fireworks event to make sure they come in in plenty of time and to make sure that they plan their journey in, but most importantly, their journey away from London. So they can enjoy New Year's Eve and then get home safe and sound," she added.

A British couple were convicted on 29 December of plotting an attack in London after the husband sent out tweets asking for advice on which targets he should hit, alerting police to a stockpile of chemicals at their home.

Mohammed Rehman, 25, and Sana Ahmed Khan, 24, were found guilty by a jury at the Central Criminal Court of engaging in the preparation of terrorist acts, with a view to hitting either a large shopping centre in the capital or the London underground network. The couple, who denied the charges, are to be sentenced at a later date.

One security expert said people should enjoy the New Year festivities but remain vigilant.

"The terror threat level in the UK hasn't changed at all. It remains as severe and it's been that way since August 2014. And to be honest, the terrorist threat level has remained pretty much at severe for the last 10 years so I think we have to treat with some caution and people should enjoy themselves and just remain vigilant and careful about what they do," said security expert David Videcette.

"We need to be aware of what has happened in Paris, and of course we need to be in a position to counter any threat that may come towards certainly London or any other city in the UK. But we have to temper that with how real is it and I think that's where we are. There needs to be sufficient numbers of armed officers, there needs to be sufficient numbers of police officers, there needs to be sufficient numbers of paramedics and other emergency services on duty to deal with something that may happen but the risk is fairly small," Videcette added.