Police have launched an investigation after a man was filmed calling a group of British Jews who attended an antisemitism march “child killers” on a London train.

A video on X/Twitter filmed on a Govia Thameslink service on Sunday afternoon also shows the man threatening to “smack” supporters of Israel “across the head” after asking one National March Against Antisemitism attendee if he supported the Jewish state.

According to the video, the man said: “My bro, you’re a bunch of Israel supporters all of you. You support f****in killers.”

He then calls the group “a bunch of killers and child molesters.” The man also called another individual a “clown” for having an Israeli flag in his possession. 

The man concludes by saying: ”F*** all of you, Free Palestine” before getting involved in a fight with another person on the train. The train was travelling towards Hertfordshire from central London at the time of the incident at 5:30pm. 

A British Transport Police spokesperson told the JC: “Detectives are investigating a racially aggravated incident on a Thameslink train from West Hampstead to Mill Hill Broadway yesterday (26 November) at around 17.30pm.

“Anyone who witnessed the incident or has information is asked to please contact the British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 528 of 26 November 2023.”

When asked about the video, a Thameslink spokesperson added: “We've passed this on to the British Transport Police to investigate.”

StandwithUsUK, a charity which educates people about Israel, who shared the video, said: “The fight against antisemitism in the UK has never been more important.”

Around 105,000 people attended the march organised by the Campaign Against Antisemitism (CAA) in central London on Sunday afternoon.

Former prime minister Boris Johnson was among the high-profile figures joining the march, a day after anti-Israel protesters also gathered in the capital to demand a permanent ceasefire in Gaza. 

Those who addressed the marchers included Chief Rabbi Sir Ephraim Mirvis and immigration minister Robert Jenrick, as organisers claimed the anti-Israel rallies in recent weeks had made the capital a "no-go zone for Jews".

The start of Sunday's march saw English Defence League founder Tommy Robinson, real name Stephen Yaxley-Lennon, arrested by police after he tried to join marchers.

Alongside Robinson’s arrest, the Metropolitan Police said a second arrest was made of a man on suspicion of making antisemitic comments.

The force said in a statement: "As the crowds left along Whitehall a man was heard to make antisemitic comments. He was arrested on suspicion of a racially aggravated public order offence.”

It comes just weeks after a London Underground driver who appeared to lead passengers in a chant of "free Palestine" on a Tube train was suspended by Transport for London (TfL).

According to social media footage, the driver of the Central Line service said "free, free" to which the passengers responded "Palestine".

The video appeared to show the chant being led over the train's speaker system.