The Metropolitan Police has warned that it is preparing for potential violence and hate speech crimes across two protests in London this Saturday.
More than 4,000 officers will be drafted in to police the rival events - possibly one of the largest protest deployment in decades - amid fears that far-right demonstrators could clash with pro-Palestine marchers if the two groups are not kept apart.
In addition, tens of thousands of football fans are also expected at Wembley Stadium for the FA Cup Final, adding further pressures on the capital's police.
Scotland Yard said the risks meant it had to impose the "highest degree of control".
Measures the Met is planning include the first authorisation of live facial recognition cameras at a demonstration. The force added it was taking the rare step of putting its armoured vehicles on standby.
Drones will also be deployed to scan for suspects, and all officers will be equipped with riot gear.
Tens of thousands are expected to join a "Unite the Kingdom" event organised by anti-Islam activist Stephen Yaxley-Lennon, better known as Tommy Robinson, as well as at the annual "Nakba Day" Palestinian protest in another part of central London.
Deputy Assistant Commissioner James Harman said he had "significant cause for concern" but the force could not ask for either protest event to be banned.
Under the law, the police can only request the home secretary to stop a march if they do not have the resources to contain a risk of serious disorder.
In this case, the Met believes they can keep both events separate and contained using their "most assertive" powers.
The £4.5m plan includes strict conditions on the routes of both events, making organisers personally responsible for the conduct of speakers on stages and authorising officers to use enhanced public order powers to stop and search potential troublemakers and disperse them out of central London.
Many of the 4,000 officers called in to police both events are being diverted from normal crime-fighting duties and 660 are arriving from other forces outside of London.
Harman said that the Nakba Day and Unite the Kingdom events were occurring amid heightened fears among both Jewish and Muslim communities but also in the wake of the national terrorism threat level being raised to its second highest rating.
"These factors give us significant cause for concern as we head into the weekend and require a policing plan that provides us with the most assertive grip on the movement of large numbers of people, large groups, and the potential for serious disorder and other criminality that may arise as a result," he said.
The first Unite the Kingdom event staged by Yaxley-Lennon last September drew at least 100,000 to London. While many of those attending saw it as an opportunity to peacefully express their interpretation of British identity, there were a series of clashes with the police and anti-Muslim hate speech incidents.
The Home Office has banned at least seven people from coming to the UK to take part in Saturday's event.
Specialist officers, working with prosecutors, will be on standby to take swift decisions to arrest and charge hate speech crimes. That may include arrests for chants referring to "intifada" at the pro-Palestine march.
"If something is hateful and intimidating we will take action whatever the academic or historical interpretation of those words," said Harman.
"We have been clear since the outset, we would not accept routes or rally locations that would increase the risk of intimidation to any particular community, or that would risk the two protests coming together."
Harman said the force would "deploy very significant resources" to keep the opposing groups apart "to keep everybody safe".
He added the armoured vehicles were "very much a contingency" that had not been used in London for a "significant period of time".
"We will not be using it unless we absolutely have to but it's there to support officers in the face of extreme violence," the senior officer added.
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