Youssef Zaghba's name was on the The Schengen Information System, a cross-European alert system

The police, MI5 and the UK border force missed at least 18 clear chances to tackle the three London Bridge jihadists raising even more serious questions about their ability to stop violent extremists.

MailOnline can reveal there were several opportunities to stop more than one of the terrorists getting into Britain in the first place - but the authorities failed to intervene.

Mastermind Khuram Butt was deemed a 'low priority' despite an aborted attempt to wage holy war in Syria, links to several notorious extremists and an appearance on national TV where he unfurled an ISIS-style flag in public.

Friends and worried parents say they reported him to the anti-terror hotline at least three times for extremist behaviour and trying to radicalise children.

The youngest attacker Youssef Zaghba, 22, was waved through at Stansted Airport in January despite Italian police flagging him as a potential terrorist on a Europe-wide warning system designed to alert passport control.

Terrorists: Khuram Butt, Rachid Redouane and Youssef Zaghba massacred seven people in a rampage which started on London Bridge on Saturday night - but the authorities misses many chances to disrupt them

Butt and his fellow murderers were shot dead inside Borough Market (pictured) and wore fake suicide vests as they ran down people with a white van and then stabbed and slashed people on Saturday night

His own mother even asked police in his native Italy to keep him in custody after he tried to fly to Syria and told officers: 'I'm going to be a terrorist'.

And failed asylum seeker Rachid Redouane, 30, was not deported after ten years in the UK despite being caught with a fake passport and living illegally under a false name.

He then married a British woman in Ireland and used it as a 'backdoor' to return to the UK and carry out the devastating attack on Saturday, killing eight and maiming 48 by ramming crowds with a rented van and slashing people with knives.

Their attack, the third in three months in Britain claiming 34 lives, has revealed a series of incredible blunders by the authorities before they unleashed mass murder.

Here are the chances they missed:

The ringleader: Khuram Butt

Khuram Butt was known to the police and MI5 but was considered a lower priority than other extremists

1. Khuram Butt publicly abused moderate Muslims who spoke out against the murder of Lee Rigby in 2013. Mohammed Shafiq, chief executive of anti-extremism group the Ramadhan Foundation, said Butt called him a 'Murtad' - traitor in Arabic - when he confronted Anjem Choudary about supporting terrorism days after the attack in Woolwich.

2. In 2015 he talked of abandoning his pregnant wife Zahrah to wage holy war in Syria but relatives talked him out of it.

3. In the same year a friend called the anti-terror hotline over his extremist behaviour and his obsession with YouTube rants by hate preachers.

He said: 'He was not arrested and was allowed to keep his passport. I did my bit, I know a lot of other people did their bit, but the authorities did not do their bit.'

4. A mother was alarmed at him bribing schoolchildren with sweets and money in the local park to listen to him speak. Others said he was going door-to-door trying to approach youngsters. She also made a call to the anti-terror hotline was made.

5. In 2016 he appeared on the Channel 4 film The Jihadis Next Door and was filmed unfurling an ISIS-type flag in Regent's Park before rowing with police called by frightened members of the public.

6. Four months later - in May 2016 - he secured a job on the Tube and had access to tunnels under Parliament with no problems.

7. He worked at Ummah Fitness in Ilford with Sajeel Shahid, 41, a member of the banned al-Muhajiroun network who was accused of helping train the 7/7 bomb ringleader Mohammed Siddique Khan.

8. His mother Fahmida Saif, 60, said she had repeatedly warned her son off 'getting involved with religious fanatics' as details emerged of his key role in hate preacher Anjem Choudary's London terror group.

9. Last year was reported to police last year for violent extremism and in July 2016 he physically and verbally abused crowds at an Eid festival.

Dr Usama Hasan, of the anti-extremist think-tank Quilliam, revealed he reported Butt to police and MI5.

He was screaming at 'everyone' including children enjoying fairground rides at a Muslim funfair in east London on July 6 last year.

He said: 'He was an al-Muhajiroun type guy, the network of Anjem Choudary and when I reported it to police I said I was pretty sure he was from that network. I said in my opinion he was a threat to national security because he was violent. He had no respect for anyone'.

10. Butt was arrested in January but was let off with a caution.

The Italian jihadi: Youssef Zaghba

11. In March 2016 the 22-year-old Italian-Moroccan had been arrested as he tried to travel to Syria from Italy on a one-way ticket and told the police: 'I'm going to be a terrorist.'

12. After the incident his mother Valeria Collina said her son was 'closely followed' in Italy and she herself had asked police to take him into custody.

13. Zaghba was briefly stopped at Stansted Airport when flying into the UK from Bologna in January this year. Border staff in the UK would automatically have been alerted about the danger he posed when he presented his passport.

Youssef Zaghba tried to flee Italy for Syria and his own mother tried to shop him to the authorities as dangerous

The terrorist's name was on the The Schengen Information System - a red flag warning system informing other European nations if criminals are trying to enter their country.

An insider told The Sun: 'Details of Zaghba's detention in Bologna in March 2016 were inserted into the Schengen Information System.

'This was consulted by British authorities when Zaghba landed in Stansted in January on a flight back to the UK from Bologna.'

14. His mother Valeria says that UK paid no attention to him while he was in Britain and claims he was only fully radicalised while living in London this year after meeting Butt

The asylum seeker: Rachid Redouane

The bodies of the two other men, including Redouane, believed to be on the right, lie in the road in Borough Market after being gunned down

15. The Moroccan-born pastry chef Rachid Redouane lived in the UK for up to ten years after claiming asylum under the name Rachid Elkhdar and claimed to be six years younger than he really was. In 2009 his application was refused but he remained in the UK illegally.

16. Months later he was arrested in Scotland, and held for several days, after attempting to travel to Northern Ireland by ferry. He was found in possession of a fake passport in this instance. Again, he was not deported.

17. After marrying Briton Charisse O'Leary in Ireland he is allowed to return to Britain. His former boss in a north London bakery says he was a known associate of extremists like Anjem Choudary – and was 'brainwashed' - but was not even on MI5's radar

18. Irish detectives are attempting to trace whether Khuram Butt, had spent any time in Dublin, including with Redouane, after Shaykh Dr Umar Al-Qadri, imam of the Islamic Centre of Ireland, said he thought he recognised the killer's face.