A pro-Palestinian activist carrying Hitler placards in the boot of his car was stopped by police before being released and allowed to rejoin the crowds just 10 minutes later.
The signs featured photos of Hitler morphing into Israeli Prime Minister Benjamin Netanyahu, with the caption "the irony of becoming what you once hated".
The placards were discovered in the car boot belonging to a man who had been wearing Palestinian flags whilst marching.
GB News spotted the man whilst he was being questioned by police during the march in London, which saw 500 officers deployed to the streets to maintain order.
Placards with Hitler's face on were discovered in the boot of a Palestinian protester's car
GB News
The man was taken away by police in a carrier but was seen in the crowd about 10 minutes later, between 3.30pm and 4pm.
Police at the scene confirmed at the time that the man had not been arrested.
Photos of the posters soon circulated online. The Metropolitan Police responded to the images on X, stating: "These photos of placards are being shared online. We believe they were taken during a proactive vehicle stop by officers near the march start point.
"As a result, we don’t believe they have been distributed. Should they be displayed in the crowd, action will be taken."
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Police let the man rejoin the crowds after 10 minutes
GB News
The force has confirmed that were 10 arrests made in total at today's protests, which comprised of two-large scale demonstrations.
The larger of the two protests, organised by the Islamic Human Rights Commission, is pro-Palestinian and takes place on the final Friday of the Muslim holiday of Ramadan.
The second demonstration is a pro-Israel counter-protest, a "static demonstration" set to be carried out in Parliament Square.
Commander Colin Wingrove, who is leading the policing operation, said: "The conflict between Israel and Hamas continues to have a far-reaching impact across communities including here in London.
Demonstrators march through London, during an Al-Quds Day rally organised by the Islamic Human Rights Commission in support of Palestinians
PA
"We recognise that there will be some who feel this march should not be allowed to take place at all.
"We work to the law. Parliament has determined that there are only very rare and specific circumstances when an application can be made to the Home Secretary for a protest to be banned. It requires a real risk of serious disorder and neither the intelligence picture nor the conversations we have had with organisers give us reason to believe that threshold will be met today.
"The rights of people to express their views through protest must be protected and our officers will ensure they are, but anyone who abuses those rights and uses them as an opportunity to commit offences or to promote hate can expect to face police action."
Prior to the marches, the police warned protestors taking part that they must not "cross the line into criminality".
