Britain will need to radically change its strategy to stop jihadi attacks because the threat is now at a “completely different” level of danger, according to the country’s top counter-terrorism officer.
Mark Rowley, the Metropolitan police assistant commissioner, said the changes could cover police, MI5, communities, technology companies, the law and other policies.
Rowley outlined his blueprint as police admitted that Khuram Shazad Butt, the London Bridge attacker pictured in a football shirt with a hoax suicide bomb belt, had been investigated in 2015 but ruled out as a potential terrorist attacker.
The assistant commissioner admitted Butt had been categorised as not posing a risk of attack two years ago.
Butt, Rachid Redouane and a third man not yet named by police hit people with a van on London Bridge and then went on to stab others on Saturday night. Seven people were killed and at least 48 were injured. The attackers were killed in a hail of 46 bullets fired by eight police officers.
The attack came after atrocities in Westminster on 22 March and Manchester on 22 May, with suspected attack plots foiled in between, one of which was by chance.
Rowley said: “In nine weeks, we’ve had five plots foiled and three successful attacks. That is completely different to anything we have seen for a long time. As the prime minister has indicated, we’re going to need to do some things differently.
“We’re going to have to think again about the next iteration of our police and security service model, which has constantly had to innovate over many decades.”
He said of Butt: “We will probably discover information on covert communications that were [not in] our knowledge that if we had access to those communications it may have changed our judgment.”
At a press briefing with questions mounting about what the authorities knew, Rowley said: “Khuram Shazad Butt was known to the police and MI5. But there was no intelligence to suggest that this attack was being planned and the investigation had been prioritised accordingly.”
Counter-terrorism sources have been warning of an increasing workload since 2014 following the rise of Islamic State and its declaration of a caliphate which 900 Britons are believed to have traveled to.
There are 3,000 people suspected of jihadi activity – Butt was in this pool – and 20,000 former suspects, who included Manchester Arena suicide bomber Salman Abedi.
Rowley said more would be asked of communities to challenge extremism, and of the private sector, believed to be a reference to internet companies. He said the new government would “want to wrestle again with legal and policy issues”.
The Met’s commissioner, Cressida Dick, warned of a “new reality” of terrorist threat after the attacks on London Bridge and Borough Market. Into this mix come fears about battle-hardened Britons returning from Isis-held territory in Syria as the terrorist group loses territory, adding to the threat.
Two of the attacks have come since the general election was called, catapulting security into the political debate.
The Labour leader, Jeremy Corbyn, backed calls for Theresa May to resign, saying: “We should never have cut the police numbers”. They fell by 20,000 while she was home secretary.
May responded that she gave police extra powers to deal with terrorism, which Corbyn had opposed when he was a backbench MP.
“Jeremy Corbyn has boasted that he has opposed those powers and opposed the powers for anti-terror actions throughout his time in parliament,” she said. “And I also support, absolutely, shoot-to-kill and I think what we saw on our streets on Saturday was how important that was.”
On Monday, 36 people remained in hospital, 18 in a critical condition.
The family of James McMullan, a 32-year-old from London, said they believed he was among the dead. His sister, Melanie McMullan, said police had found his bank card on a body at the scene.
It emerged that Christine Archibald from British Columbia in Canada died in the arms of her fiance, Tyler Ferguson. The French government confirmed that a French man was killed and French media reported that seven people from France were injured, four of them critically.
Crowds gathered outside City Hall for a vigil for the victims on Monday night where the London mayor, Sadiq Khan, the home secretary, Amber Rudd, and shadow home secretary, Diane Abbott, laid white roses.
The investigation into the attacks involved two more raids on Monday in Newham and Barking, east London, as police tried to establish if the three attackers had any help. The Renault van used to stage the attack was hired just before the attack, police said. . Police said all 12 people arrested following the attacks were released without charge.
Police named the second attacker as Rachid Redouane, 30, who claimed to be Moroccan and Libyan. He was not known to police and MI5 before the attack on Saturday. The third attacker has not been named.
Butt is reported to have associated with al-Muhajiroun, the banned extremist group whose leader Anjem Choudary has been linked to the recruitment of more than 100 British terrorism suspects. He featured in a Channel 4 documentary about British jihadis and was thrown out of a mosque in Barking for repeatedly challenging the imam.
Rowley said he had seen nothing to suggest mistakes were made in assessing the danger Butt posed in 2015, despite a member of the public complaining about him to the anti-terrorism hotline.