Isis has claimed responsibility for the attack in which the men ploughed their van into pedestrians on London Bridge before launching an indiscriminate knife attack at people in the Borough Market area.
Reports claim one of the killers, believed to be a 27-year-old from Watford living in Barking, appeared in a Channel Four documentary where he was filmed arguing with police after he displayed an Isis flag in Regent’s Park.
He appeared on camera alongside two notorious hate preachers who were both well known to the authorities.
An acquaintance of this man claimed to have raised the alarm after becoming concerned he had been radicalised by watching extremist YouTube videos.
Others told reporters police were warned two years ago the suspect was becoming fanatical and attempting to radicalise children in the park.
Speaking to the BBC’s Asian network, an unnamed man said the suspect had shown signs of extremism over the past two years.
“He used to listen to a lot of Musa Jibril. I have heard some of this stuff and it's very radical.
“I am surprised this stuff is still on YouTube and is easily accessible.
“We spoke about a particular attack that happened and, like most radicals, he had a justification for anything - everything and anything.
“I phoned the anti-terror hotline. I spoke to the gentleman. I told him about our conversation and why I think he was radicalised.”
He said no action was taken.
“I did my bit... but the authorities didn't do their bit”.
Neighbours in Kings Road, Barking told reporters yesterday that the suspect appeared to be an unassuming family man nicknamed Abz who had worked for KFC, Topshop and the London Underground.
One neighbour said he gave the appearance of being "a good Muslim".
He was said to be well-known in the local community and to have had a partner and "at least two children". He was often seen playing football with children who lived in the area as well as his own and neighbours said he would regularly wear an Arsenal shirt.
A picture of the terrorists lying dead after they were gunned down by armed police showed one of the suspects wearing the Arsenal away strip beneath his camouflage gear.
The manager of the Jabir Bin Zayd Islamic Centre in Barking reportedly claimed he had banned the suspect from attending after he aggressively interrupted the Imam to claim voting in the general election was “un-Islamic”.
Eyewitnesses said the terrorists shouted, “This is for Allah” as they went on their deadly rampage on Saturday night.
Isis is said to have urged extremists to run over civilians in a poster released over the weekend featuring a knife, a gun and a lorry which urged radicals to “gain benefit from Ramadan.”
Commissioner of the Metropolitan Police, Cressida Dick, told the Today Programme: “Inevitably with a large database on occasion some people will get through and be successful."
She confirmed the identity of the killers would be released “as soon as operationally possible.”
Police have confirmed seven women aged 38, 49, 60, 19, 27, 24 and 53 and four men, two aged 55, and two aged 52 and 27 were arrested at two addresses in Barking.
Four properties in total are being searched. As well as the flat in Barking, properties in Newham and East Ham have been raided.
Irish broadcaster RTE reported authorities found an Irish identity card on the body of one of the suspects, believed to be of Moroccan heritage, indicating he had previously lived in Ireland.
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