Speaking to the BBC, the man, who’s identity has been protected, claimed he had “done his bit” for the community in trying to stop the killer.
The man said that he had spoken to the anti-terrorist hotline about fears the terrorist had been radicalised but saw no reaction to his report.
He said: “Two years ago we spoke about a particular attack that happened and like most radicals he had a justification for anything, for everything and anything.
“And so that day I released that I needed to contact the authorities. I phone the anti-terrorist hotline, I spoke to the gentleman, told him why and how.
The man who knew the London attacker claimed he reported him to the terrorist hotline
“I told him about our conversation and how I think he’s been radicalised and basically you know just doing my bit.”
When asked what came of his effort to call the anti-terrorist hotline, the man admitted “nothing, absolutely nothing”.
He added: “They didn’t get back to me, nor was he arrested or you know, just picked up for any kind of questioning.
“He was thrown out of a mosque maybe over a year and a half ago, his local mosque, because of his radical views.
“He had an altercation at some festival where he had a table to invite people to his religion.”
The man said that he was not surprised that the person he knew attacked people in London on Saturday evening.
“I wasn’t surprised in the sense that because of, you know, his radical views, but there was still a little hope in me that it wasn’t him because this is very, very hurtful to his community,” he replied.
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“I mean the Muslims, the Muslim community in general, get a lot of criticism over how we don’t root out extremism in our community.
London terror raids Sun, June 4, 2017
Police have raided a block of flats in Barking in connection with last night's London Bridge terror attack.
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As police continue their investigations following the June 3 terror attacks, a block of flats in Barking is raided for possible suspects
“I did my bit, I know a lot of people did, but the authorities didn’t do their bit and that’s what’s shocking.
“That’s what hurts me really because this is just giving a bad name for my community now.”
Seven people were killed, and 48 injured, in the terror attack in London, before the three suspected attackers were killed by police at London Borough Market.
Properties in Barking, East Ham and Newham, have been subject to police raids with a number of arrests made.