Thousands of protesters are set to descend on Parliament Square this evening for the annual bonfire night protest lead by the hacktivist collective Anonymous.
Hundreds of riot police are due to be on stand-by as protesters - known for their Guy Fawkes masks - collect to march on the Houses of Parliament in the Million Mask March.
The protest, which is taking place in hundreds of cities around the world and at 22 events in the UK, takes place annually to make a stand against mass surveillance, austerity and infringement of human rights.
The group has called for a “MASSIVE Anonymous blockade of London City. Complete physical GRIDLOCK. Only thing that gets through are Fire & Rescue and ambulances. NOTHING ELSE MOVES.”
A message on the UK Anonymous website reads: “In 2014, we will once again march on the Houses of Parliament in London, as will we in 2015, leading up to 2016 when November 5th falls on a Saturday!
“The standard has now been set, next year we will have bigger banners, louder voices, more fireworks, more people and a louder sound system!”
"We’re gonna do what Germany did to take down the Berlin Wall," it adds.
A video posted by the protest group shows the Houses of Parliament and warns: “We pose a significant threat to you.”
In a statement, the Metropolitan Police said officers had attempted to contact organisers of the event "without success".
It added they have imposed Section 60AA of the Criminal Justice and Public Order Act 1994 across Westminster between 5pm and 2am tomorrow, which provides powers to remove masks when police fear a crime will be committed.
Last year more than 2,000 people attended, including Hollywood star-turned political commentator Russell Brand, but police fear this year’s march could attract a higher turn-out.
Brand, who is already calling for his own political 'Revolution', has urged his followers to attend the event.
Last year, a fire was started at the Victoria Memorial - close to the gates of Buckingham Palace - and protesters threw glass bottles during clashes with officers in riot gear. A video emerged late on Tuesday evening showing the protesters laying in front of a bus and goading the police (see below).