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Scotland Yard has warned of the risk of violence at a bonfire night protest in central London organised by activist group Anonymous.

Thousands of demonstrators are expected to descend on Trafalgar Square and Westminster on Thursday evening for the so-called Million Mask March.

Police have now warned that commuters could face disruption getting home from work as they announced a series of restrictions on the event, which up to 18,000 people are said to be planning to attend.

Chief Superintendent Pippa Mills warned ahead of the now annual event: “This year we have strong reason to believe that peaceful protest is the last thing on the minds of many of the people who will come along.”

Last year, activists wearing ‘V for Vendetta’ masks attacked a woman allegedly because she had “the wrong accent”.

Police said buses were “physically rocked” by protesters, people jumped onto car bonnets and police officers were attacked during the demonstration.

Chief Superintendent Mills said: “Last year hundreds of people on their way home from work, or out enjoying an evening in the capital, were surrounded by people causing them huge concern.

“Buses were physically rocked, people jumped on car bonnets, as well as serious disorder in central London and damage to a number of buildings.”

She added: “It is unacceptable that a small minority should believe they have the right to break the law, harass people, damage buildings and attack police officers.

“My message to those people planning on attending on Thursday night is if you want to take part in peaceful protest that is your right and we want to work with you. If you want to break the law then we will police you. Where offences are committed we will investigate them and make arrests."

Scotland Yard said it has “such serious concerns” about the event that it has imposed a string of conditions on it under the Public Order Act.

Interactive map of restrictions on protesters by the police

They include static protests being restricted to Trafalgar Square, the centre of Parliament Square and the area within the barriers on the East Footway of Whitehall, opposite Downing Street.

The conditions also require that any march stays within the bounds of Trafalgar Square; Northumberland Avenue; Victoria Embankment; Bridge Street; St Margaret Street; Abingdon Street; Millbank (up to junction with Great Peter Street); Great Peter Street (up to junction with Great Smith Street); Broad Sanctuary; Parliament Square; Parliament Street; and Whitehall.

Police also said the conditions mean the demonstration can only be held between 6pm and 9pm on Thursday.

In a statement on Facebook, the march's organisers said: "This November 5th, the Anonymous UK collective will again descend on central London.

"We have seen the abuses and malpractice of this government, and governments before it, we have seen the encroaching destruction of many civil liberties we hold dear, we have seen the pushes to make the internet yet another part of the surveillance state, we have seen the government's disregard for migrants, for the poor, the elderly and the handicapped, we have seen the capital, profit and greed of the few put before the well-being of the many and we say enough is enough.

"We invite all the activists, the workers, the students, all doctors, nurses and all those that want to see a positive change in the world, to join us, in Trafalgar Square from 6pm, November 5th. The government and the 1% have played their hand, now it is time to play ours."