One of the three men who carried out the London Bridge terror attack had reportedly appeared in a Channel 4 documentary about jihadis in the UK.

The 27-year-old, said to be from Barking in east London, was pictured lying on the ground after police swooped on the attackers on Saturday night and shot them dead in a flurry of 50 bullets.

Seven people were killed and 49 injured when the trio rammed a van into pedestrians on London Bridge before stabbing revellers in bars in the nearby Borough Market.

The attacker, whom police have requested not be named apart from his nickname ‘Abz’, appeared to pray to a black flag associated with Islamist groups in a London park in a Channel 4 documentary about the behaviour and motivations of British extremists.

Police are searching four houses in Barking and have made 12 arrests as part of their investigation into the atrocity.

His neighbours said the Arsenal fan had been wearing the club's replica away shirt the day before the attack, matching the one worn by one of the suspects pictured lying on the ground with what appear to be canisters taped around his body.

Neighbour Ikenna Chigbo said the attacker had asked him where he could get a van just before the attack. “He was just asking me all the details — how much was it, and just like asking where he could get a van, basically,” he told The Sun.

Another neighbour, Furqan Nabi, also said the dead attacker had asked him about hiring a van but was “a bit vague about why he wanted it”.

The Metropolitan Police said the white Renault van that mounted the pavement and hit pedestrians during the incident had recently been hired by one of the attackers.

London Bridge Terror Attack Show all 16 1 /16 London Bridge Terror Attack London Bridge Terror Attack Armed police on Borough High Street as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Armed Police talk to members of the public outside London Bridge Hospital as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Police Officers outside the Barrowboy and Banker Public House on Borough High Street as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Armed Police talk to members of the public outside London Bridge Hospital as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Armed police on Borough High Street as police deal with a 'major incident' at London Bridge PA London Bridge Terror Attack Emergency services near the scene of the incident Screengrab London Bridge Terror Attack People run down Borough High Street as police are dealing with a "major incident" at London Bridge Reuters London Bridge Terror Attack Emergency services arrive at the scene near Borough market at London Bridge Carl Court/Getty Images London Bridge Terror Attack Emergency personnel on London Bridge as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Police sniffer dogs on London Bridge as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack A second helicopter lands on London Bridge as police are responding to three incidents in the capital, amid reports that a vehicle collided with pedestrians on London Bridge, Scotland Yard said. Officers are dealing with reports of stabbings in Borough Market, where armed officers attended and shots were fired. They are also at an incident in the Vauxhall area PA London Bridge Terror Attack Police attend to an incident on London Bridge in London REUTERS London Bridge Terror Attack Police attend to an incident on London Bridge in London, Britain Reuters London Bridge Terror Attack A police officer escorts members of the public to safety at London Bridge Getty Images London Bridge Terror Attack Police attend to an incident on London Bridge in London, Britain Reuters London Bridge Terror Attack Police attend to an incident near London Bridge in London, Britain Reuters

Ken Chigbo, who lived in the same block of flats as the attacker, told The Mirror the suspect was “really sociable” and would “preach to young Muslims at the flat, sometimes up to six people quite regularly”.

A former friend of one of the attackers told the BBC’s Asian Network he had contacted the authorities after he became concerned about his friend’s extremist views.

The terrorist had been radicalised watching extremist videos online, he said, adding: “We spoke about a particular attack that happened and like most radicals he had a justification for anything and everything and that day I realised I needed to contact the authorities.”

However, the attacker was not arrested and no further action taken, he says. “I did my bit, I know a lot of other people did their bit, but the authorities did not do their bit,” he said.

A scene in The Jihadis Next Door shows a group of extremists, one of whom is believed to be 'Abz', appearing to pray to the flag as it is unfurled in a London park.

One eyewitness of the attack, named only as Gerrard, told the BBC he saw a man with stab wounds on the floor, before then witnessing three men repeatedly stabbing a girl at Borough Market.

“I was walking up to London Bridge, going past the Natwest Bank, and next thing, I saw a geezer on the floor going ‘I’ve been stabbed’. He’s got blood all down him. His mate comes past saying some[one] stabbed his mate.

“Next thing, I saw three Muslim guys with knives, they started stabbing this girl. There were three of them. I was defenceless, I could do nothing. They attacked her. […]. She was shouting ‘Help me’.

“They stabbed her I don’t know how many times. Ten times, maybe 15 times. I tried to throw bottles at them. I tried to throw a bike at them. But I couldn’t do nothing.”

Alex Shelham, who was in the Mudlark pub situated just off London Bridge with his girlfriend and friends, said they saw a woman who entered the venue “bleeding heavily from the neck”.