The attacker shot dead on London Bridge was known to police and had connections to terror groups.
The man, who was wearing a fake suicide vest, killed two people and injured three in the attack.
He has not yet been named.
The attacker was a convicted terrorist with previous links to al-Muhajiroun, the group led by Anjem Choudry and dubbed Britain’s “most prolific and dangerous extremist group”, The Independent understands.
Al-Muhajiroun was regenerating after a number of supporters were released from prison, this website reported in February.
The assailant had been recently released from prison and was being monitored by police.
The Times reported the attacker was attending a Cambridge University conference on prisoner rehabilitation being held at Fishmongers’ Hall and had threatened to blow up the building.
The Ministry of Justice (MoJ) has ordered a review into the attack having learnt of the perpetrator’s identity soon after it took place, the paper further reported.
A maintenance worker who witnessed the attack said: “Some of the guys who were on top of him were ex-prisoners and they had all been in the Fishmongers’ Hall.”
Speaking before he chaired a meeting of the government’s emergency Cobra committee, Boris Johnson said he had “long argued” that it is a “mistake to allow serious and violent criminals to come out of prison early and it is very important that we get out of that habit and that we enforce the appropriate sentences for dangerous criminals, especially for terrorists, that I think the public will want to see”.
The reports came only two hours after Cressida Dick, the Met commissioner, said her officers were working “full tilt” to gain more information about whether the attacker was known to police and was operating alone.
