British intelligence officials have denied they were warned that one of the London attackers “wanted to be a terrorist,” as CCTV footage shows the trio attempting to kill police before they died.

They rushed at armed officers who arrived in Borough Market as they struck down another victim on Saturday night, but were shot dead within seconds.

Police have been hailed for their bravery in approaching who they feared to be suicide bombers, before the vests they were wearing were found to be fake.

But British intelligence services have come under scrutiny over revelations that ringleader Khuram Butt was cautioned over an extremist assault, and known for associating with Anjem Choudary’s network of Islamists.

A cousin of Butt's wife said he openly supported Isis among the family, claiming the group’s atrocities were “quite justified” and watching extremist sermons on YouTube.

Fahad Khan said the terrorist discussed taking his family to join Isis in Syria, but was dissuaded because his wife was pregnant at the time.

Pressure increased after Italian authorities claimed they also warned MI5 over his accomplice Youssef Zaghba, who was stopped in Bologna airport at he attempted to travel to join Isis in Syria last year.

CCTV footage police shows police open fire on London Bridge attackers

The 22-year-old was stopped at Stansted in January as a result of an alert on the Schengen Information System (SIS), but officials told The Times it suggested he was wanted for a criminal matter rather than extremism.

They claimed the alert did not include the fact Zaghba told Italian police he “wanted to be a terrorist”. The extent of information uploaded to a second database used by European intelligence agency is unclear.

He was able to make multiple trips between the UK and his mother’s home in Bologna, despite the SIS alert and heavy monitoring by Italian police.

The country’s police chief said his force has its “documents and conscience clear” but understood how Zaghba slipped through the cracks.

Franco Gabrielli added: “We can understand the concern, the suffering and the difficulty of those who are called to manage complicated situations.”

Italian prosecutor Giuseppe Amato said there was not enough evidence to arrest or charge the attacker when he was caught at Bologna airport.

“We did everything we could have done, but there weren’t elements of proof that he was a terrorist,” he added.

Investigators confiscated Zaghba's computer but said it did not contain proof of a crime, although Isis propaganda was reportedly found on one of his devices.

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The terrorist, born in the Moroccan city of Fez in 1995, was estranged from his father but lived in the country for much of his life.

Able to move round the EU as an Italian citizen, he moved to the UK in 2015 and lived in Ilford while working in a Pakistani restaurant in east London.

​Zaghba also taught children at Catleaps Gymnastics in Dagenham, where managers said he did not need a background check because of his status as a volunteer and was supervised at all times.

His mother said she believed he was radicalised in London, while associating with the “wrong kind of people”.

The Metropolitan Police claimed Zaghba “was not a police or MI5 subject of interest,” although the statement is believed to have been carefully worded.

It admitted Butt, a former Tube worker and KFC employee, was known to them, but that 30-year-old accomplice Rachid Redouane was not on the security services’ radar.

The way the trio met remains unclear, but a European intelligence official told the New York Times Zaghba was introduced to Butt by an Italian faction of Al-Muhajiroun.

He and Redouane appear to have been friends, reportedly being seen together at a café next to a betting shop in Newham.

Images provided by Met Police of (left to right) Khuram Butt, Rachid Redouane and Youssef Zaghba

The pastry chef also used the surname Elkhdar and Rachid al-Magrabi, and there were reports he had fought against Muammar Gaddafi’s forces at the start of the Libyan civil war in 2011.

Both Butt, whose family were from Pakistan, and Redouane lived in nearby Barking, where both had young children.

Redouane, who claimed to be from both Morocco and Libya, had been denied asylum in the UK in 2009 but moved back to London after gaining an EU residency card by marrying a woman in Ireland.

“While she was at work he used to come here with friends,” a neighbour told The Sun.

“I think they used the flat to plan the attack […] on Saturday he was here with Khumar Butt.”

CCTV footage captured the trio laughing, joking and hugging at a gym in Ilford five days before the atrocity.

Butt, Redouane and Zaghba gathered shortly after midnight on 29 May at the Ummah Fitness Centre.

Redouane left his mobile phone on a pile of building materials before they disappeared for around 10 minutes, suggesting the plotters were wary of surveillance.

The Ummah Fitness Centre in Ilford where the three attackers met days before the atrocity (AFP/Getty Images)

Ummah Fitness Centre, which operates a gender-segregated timetable and remains open until 3am for fasting Muslims during the holy month of Ramadan, said it was “shocked and saddened” by the London Bridge attack.

“While Mr Butt did occasionally train here at UFC gym, we do not know him well nor did we see anything of concern. We will of course help the police in any way we can,” said a statement posted on its door.

The gym, whose name refers to the Muslim community, could not be reached to confirm reports that Butt ran its mixed martial arts classes.

A member of the Ummah Fitness Centre, who said Butt had enrolled him three weeks ago, reported that he looked troubled in the lead-up to the attack.

The man said Butt would normally be friendly, greeting him when he arrived for sessions, but increasingly appeared “blank”.

“He was very quiet as well, he was not speaking with strangers,” he added.

“He speaks only with his guys, people with robes […] I last saw him two weeks ago. Sometimes when you spoke with him he would not respond to you, he was blank.

“The first time I saw him in the gym he was not like that, he was normal. But after a couple of days he was worried about something, but I don't know what about.

"When I spoke with him he wasn’t responding."

The gym is reportedly run by Sajeel Shahid, who has been named as a senior member of Choudary’s banned extremist network Al-Muhajiroun by FBI agents.

People view flowers and tributes near the scene of the London Bridge attacks (Getty Images)

An extremist-turned supergrass said Shahid and his brother helped set up terror training camps in Pakistan and safe houses for British jihadis.

Among the graduates was the ringleader of the 7/7 attacks, Mohammed Siddique Khan, while Shahid was also named in the trial of seven plotters who attempted to bomb the Bluewater Centre and Ministry of Sound.

Fresh arrests were made in Ilford overnight, where armed police detained two men on a street and a third during searches of a home.

Two of the men, aged 27 and 29, were arrested on suspicion of the preparation of terrorist acts, while a 33-year-old was arrested on suspicion of possession with intent to supply controlled drugs.

They are among a total of five suspects in custody as searches continue at the house and an unidentified “business address” in Ilford, believed to be the Ummah Fitness Centre.

Witnesses reported that computer equipment had been taken away from the gym, with the road cordoned off as plain-clothed police took evidence away.

Isis has claimed responsibility for the attacks in London Bridge, Manchester and Westminster, having released detailed instructions on how to carry out massacres using vehicles and knives.

An issue of the group’s Rumiyah propaganda magazine published on Thursday hailed Butt, Redouane and Zaghba as “Islamic State soldiers,” giving them the war names of Abu Sadiq al-Britani, Abu Mujahid al-Britani, and Abu Yusuf al-Britani.

All eight people killed in the massacre have now been officially identified, while a further 10 victims remain in a critical condition in hospital.