The major police operation has cost the police £4.5million, with 4,000 officers on duty.
The force aims to avoid clashes between the two rallies.
It is estimated that around 50,000 people will march in the Unite the Kingdom rally, organised by Tommy Robinson.
The pro-Palestinian Nakba Day rally is expected to draw 30,000.
Crowds gathered at around 10am, waving Union flags in what organisers deemed as “the greatest patriotic display the world has ever seen”.
Armoured cars, facial recognition, drones and horses have been deployed as the Metropolitan police launches an ‘unprecedented’ response
Daniel Kebede, National Education Union general secretary, said “we’re marching today to show that we will not allow Tommy Robinson and the far right to divide our communities”.
In a post on X on Saturday, he said: “The Unite the Kingdom march organisers are spreading hatred and division.
“They do not reflect the Britain I’m proud of. Peaceful protest is a fundamental right and one I will always protect. But if protest turns violent, we will act swiftly, with extra court capacity in place.”
Two men who arrived in London to attend the Unite the Kingdom protest have been arrested in the vicinity of Euston station over an unrelated incident in Birmingham, police said.
It is estimated that around 50,000 people will march in the Unite the Kingdom rally, organised by Tommy Robinson
The Metropolitan Police posted on X saying: “Two men, wanted on suspicion of GBH following an incident in Birmingham where a man was run over, were spotted arriving into London to attend the UTK protest.”
The Crown Prosecution Service (CPS) said the revised advice is designed to reflect “the changing international context” and follows separate guidance concerning the fast-tracking of hate crime prosecutions issued earlier this month.
The guidance tells prosecutors to take account of the wider context surrounding protests, including heightened tensions linked to national or international events.
Recent criminal cases have seen suspects charged after shouting “death to the IDF (Israel Defence Forces)” and “globalise the intifada”.
The Government has also blocked 11 foreign nationals described by Sir Keir Starmer as “far-right agitators” from entering the UK ahead of the Unite the Kingdom rally.
Speaking during a visit to a Metropolitan Police command centre in Lambeth on Friday, the Prime Minister criticised the Unite the Kingdom organisers for “peddling hatred and division, plain and simple”.
Sir Keir Starmer carried out his visit to Lambeth alongside Met Commissioner Sir Mark Rowley and London Mayor Sir Sadiq Khan before today’s rallies.
Sir Mark, seated in front of live CCTV images of different parts of the capital, told the PM: “We’ve got a time when hate crime has been escalated for the last two or three years.”
He added: “And then ‘small p’ politics and protest groups who have got more polarised and angry, and so both groups at the weekend have a track record of having an intimidatory effect on the communities.”
