Scotland Yard is preparing to deploy thousands of extra officers in a bid to crack down on an annual protest against state surveillance incursions, amid fears demonstrations will turn violent.
Today's Million Mask March, organised by hacktivist collective Anonymous, is a yearly event that sees crowds descend on major city centres, many clad in the famed 'V for Vendetta' mask associated with their movement's figurehead, Guy Fawkes.
The protest has previously sparked violent scuffles between protesters and police, and 2015's march is tipped to be the biggest yet - with 20,000 people anticipated to flood central London, and hundreds of thousands more in other capitals across the world.
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Fearing large-scale civil unrest, damage to monuments and attacks against officers, the Met has locked down Westminster and placed strict conditions on the event.
Officer numbers have been beefed up to manage scuffles like last year's, and police are imposing severe restrictions on the march route and where protesters will be permitted to remain stationary, including around Parliament Square.
Static assembly will only be allowed between 6 and 9pm in the tourist hotspot Trafalgar Square, a small section of Whitehall opposite Downing Street, and on the lawns outside Parliament.
A fringe group of protesters has already announced plans to protest outside the Ecuadorian embassy, where Wikileaks founder Julian Assange is seeking refuge from extradition, under the guise of demonstrating to "free Robin Hood".
They too will be wearing 'V for Vendetta' masks, while clad in black robes and full, shoulder-length white judges wigs.
Chief Superintendent Pippa Mills has spoken out ahead of the Bonfire Night 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.
She claimed that in 2014 "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".
But her comments were rebutted by the march's organisers in a statement on Facebook, who said the event was to call for a "positive change in the world".
"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," they wrote.
"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."
They invited fellow activists, workers, students, doctors and nurses - and "all those that want to see a positive change in the world", to join them on the November 5th march.
"The government and the 1% have played their hand," they concluded, adding: "Now it is time to play ours."