But he said there was an “arguable” breach of the state’s duty to protect life by the failure to place protective barriers on London Bridge, where two people were killed by a van driven by the attackers.

Lucraft said no formal physical security measures were installed on London Bridge despite it being a location that was particularly vulnerable to a vehicular attack. “There were weaknesses in systems for assessing the need for such measures on the bridge.”

He described the MI5-led pre-attack investigation into Butt as “thorough and rigorous”.

“I am not persuaded that investigation opportunities were lost which realistically could have saved lives,” he said.

He also criticised Butt’s family, who he said were aware of his extremist views but did not report him to the authorities.

Family members of the victims were critical of the authorities for not recognising the danger posed by Butt and not bolstering physical security in the area.

Philippe Pigeard, whose son Alexandre was stabbed to death, told The Guardian his life had been destroyed and he believed more could have been done by the authorities.

“The question is: could this attack have been prevented?” he said. “The answer is really difficult but, yes, probably. I think they could have done a better job.”

Christine Delcros, girlfriend of victim Xavier Thomas, said: “I believe this attack was preventable.

“I find it staggering that [Khuram] Butt, a well-known extremist was allowed to work within the London Transport network, to have access to and teach young children, and to rent and use a vehicle in a manner now too often encountered. I am dismayed SO15 [Counter Terrorism Command] did not pass this critical information to any of his employers.”

Thomas’s parents, Christiane and Philippe Pesez, said that key clues to the attackers’ plan were missed. “There had clearly been many opportunities to link [Butt] to both other accomplices – we believe opportunities that were missed and lost,” they said.

Lucraft ruled all eight victims were unlawfully killed as he delivered his conclusions following weeks of evidence, including from bereaved families who challenged the authorities over whether more could have been done.

On June 3, 2017, three terrorists drove a rented van into pedestrians walking on London Bridge, killing two people. They then ran amok with 30cm (12in) knives in a stabbing rampage that killed six people.

The attack lasted 10 minutes and ended when armed police shot dead the terrorists, all three of whom had fake suicide bomb belts wrapped around them. Police fired 46 shots at the terrorists to end the UK’s first “marauding” attack, where perpetrators run through a crowded area.

The ringleader, Khuram Butt, 27, had been under MI5 investigation since 2015 over fears he would stage an attack. Eventually, he struck alongside fellow east Londoners Rachid Redouane, 30, and Youssef Zaghba, 22.

The inquests heard of alleged failures by MI5 to search for clues to the atrocity Butt was plotting, but the security services and police insisted the attack could not have been prevented.

The van first struck Xavier Thomas, 45, who was thrown over the side of the bridge into the River Thames. It took three days to recover his body.

The next victim was Christine Archibald, 30, a Canadian who was walking with her fiancée when the van drove into her. Rented hours earlier, the van crashed to a stop against railings by a pub and overlooking the courtyard of the Boro Bistro restaurant.

The terrorists, who had knives taped to their hands, started a running rampage in which they stabbed six people to death.

Those victims sustained horrifying injuries. Sébastien Bélanger, 36, was a head chef at a nearby restaurant; Alexandre Pigeard, 26, a waiter from France, tried to save someone else as he lay dying; Kirsty Boden, 28, a nurse from Australia, was killed after tending to the wounded; Ignacio Echeverría Miralles de Imperial, 39, from Spain, was killed as he tried to fight the terrorists armed with a skateboard; James McMullan, 32, from Hackney, East London, had been in a pub watching the Champions League final; and Sara Zelenak, 21, an Australian, was on a night out after being given time off from her au pair work at the last minute.

The inquest heard the terrorists may have originally planned to attack Oxford Street and had wanted to use a 7.5 tonne truck, similar to earlier vehicle attacks in Europe, which would have almost certainly caused more carnage.

The attack was one of several in the UK in 2017. In March, a vehicle was driven into pedestrians on Westminster Bridge, with the terrorist fatally stabbing a police officer guarding the Palace of Westminster. Then, in May, the Manchester Arena was struck by a suicide bomber who killed 22 people at a pop concert.

Terror inquest hears details of 2017’s deadly London Bridge attack

After the London Bridge attack a rightwing extremist attacked worshippers with a rented van near a north London mosque, and in September there was an attempt to bomb a London tube train with a device that failed to fully ignite.

The inquest heard of incredible savagery by the attackers who hunted as a team, stabbing many around the neck area, and of desperate scenes as Saturday revellers found themselves in a nightmare, with some trying to save others from being murdered.

A nurse, Helen Kennett, came face to face with the terrorist Redouane and challenged him. She told the inquest: “I looked at him and I said: ‘What’s wrong with you?’ And he looked at me and said: ‘No, what’s wrong with you?’ … He stabbed me in the neck on the left side.”

She had gone to help Pigeard, and said to the dying waiter: “Let me help you, I’m a nurse.” She told the inquest: “He shook his head … I am sure he told me to run.”

The Guardian understands that MI5 did have “eyes on” surveillance on Butt at times and did see him associating with his two accomplices but did not appreciate their significance or the murder they were plotting.