The Metropolitan Police have defended a decision to downgrade an inquiry into one of the men who carried out Saturday night’s terror attack.
They said Pakistan-born Khuram Butt, 27, of Barking, London, was known to police and MI5 in 2015, but there had been no evidence of a plot.
The two other perpetrators were not known to security services.
All 12 people arrested on Sunday after the London attack have now been released without charge.
Two of the three men behind the attack, in which seven people were killed and 48 injured have been named by police.
The other attacker was Rachid Redouane, 30, from Barking, who police said had claimed to be Moroccan-Libyan. He was a chef, who also used the name Rachid Elkhdar.
All three men were shot dead by police within eight minutes.
The attackers drove a hired van into pedestrians on London Bridge before stabbing people in the area around Borough Market.
Metropolitan Police assistant commissioner Mark Rowley said an investigation into Butt began in 2015, but “there was no intelligence to suggest that this attack was being planned and the investigation had been prioritised accordingly”.
The inquiry was “prioritised in the lower echelons of our investigative work”, Mr Rowley added.
Asked if that had been a poor decision, Mr Rowley said he had seen nothing yet to suggest it, according to the BBC’s home affairs correspondent, Danny Shaw.
At any one time there are around 500 active counter-terrorism investigations concerning 3,000 people of interest.
Mr Rowley said work was continuing to understand more about the attackers, “their connections and whether they were assisted or supported by anyone else”.
TV Jihadist
Butt featured in a Channel 4 documentary last year about Islamist extremists with links to the jailed preacher Anjem Choudary.
The married father-of-two could be seen in the programme arguing with police officers in the street, after displaying a flag used by IS in a London park.
Two people in Barking, east London, had also raised concerns about Butt, the BBC’s home affairs correspondent Dominic Casciani said.
One man called the anti-terrorism hotline in 2015, and a woman went to the local police because she was scared Butt was trying to radicalise her children.
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