Security services missed vital clues in the days leading up to several of the terror atrocities that have hit Britain this year, it has been revealed.

It is now thought that 35 lives could have been saved at Manchester, London Bridge and Westminster if police had correctly acted on intelligence.

Detectives had intelligence about Manchester bomber Salman Abedi in the months before his attack killed 22 adults and children outside an Ariana Grande concert, David Anderson QC found.

The information would have caused an investigation into him to be opened 'had its true significance been properly understood', the review said.

It also emerged that a meeting to discuss Abedi's threat level was due to be held a week after he carried out his deadly bombing.

The review also revealed that London Bridge attacker Khuram Butt was being actively investigated by security services at the time of his attack and Westminster terrorist Khalid Masood scoped out the bridge days before he drove a car along its pavement, killing tourists.

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Manchester bomber Salman Abedi was flagged up to security services before his attack killed 22 people including children at an Ariana Grande concert

An independent review of the counter-terrorism performance by British police and intelligence services suggests the deadly suicide bombing at Manchester Arena might have been prevented if information had been handled differently

The review, published today, discloses that three terrorists involved in four attacks that hit Britain between March and June this year had at some point been on authorities ' radar.

Manchester attacker Abedi was identified by a 'data-washing exercise' as falling within a small number of former subjects of interest who merited further consideration.

However, a meeting scheduled to consider the results of this process had not been held at the time of the bombing. It was due to take place a week later.

Reviewer Mr Anderson says: 'It is conceivable that the Manchester attacks in particular might have been averted had the cards fallen differently.'

An opportunity was also missed to place Abedi on 'ports action' after he travelled to Libya in April. Despite the issues raised, MI5 says the attack would not have been thwarted had more investigation been carried out.

Attacks at Westminster, Manchester, London Bridge, and Finsbury Park killed and injured dozens of people between March and June this year.

MI5 and police launched independent reviews to examine what was known about the terrorists before they struck and the review of those investigations was published today.

Khuram Butt, who led the three-strong gang behind the London Bridge van and knife attack in June, was the principal subject of an MI5 investigation from mid-2015 until the date of the deadly assault.

Three terrorists lie dead in Borough Market after a van and knife attack on London Bridge. The ringleader, Khuram Butt, was being investigated at the time of the atrocity

Butt was previously thought to have been planning an attack, but an operation examining him was suspended due to other priorities. Fellow London Bridge attacker Youssef Zaghba was flagged up by Italian authorities but an email to UK security services was missed

Three THOUSAND terror suspects being tracked by authorities The scale of the threat facing the UK was laid bare in today's report. It revealed counter-terror teams are running about 500 live investigations involving 3,000 individuals at any one time, while there is also a wider pool of 20,000 subjects previously looked at who must be kept under review. A total of nine Islamist terrorist plots have been thwarted in the UK over the past year, the director general of MI5 has told Cabinet earlier today. And it emerged 22 potentially deadly plans have been thwarted since Drummer Lee Rigby was murdered near his barracks in Woolwich in south London in May 2013. Meanwhile, Home Secretary Amber Rudd told MPs that Islamic State (IS) jihadis fleeing defeats in the Middle East are plotting attacks in the West. The scale of the current threat facing the UK is seen as unprecedented. Advertisement

Butt was also tracked by Operation Hawthorn, but that was suspended due to lack of resources. The Operation was resumed on the day he attacked.

The report stated: 'From mid-2015 until the date of the attack, Khuram Butt was the principal subject of Operation Hawthorn, an MI5 investigation which was opened following information suggesting that he aspired to conduct an attack in the UK.'

'From late 2015 to early 2016 there was no further indication of attack-planning, and Khuram Butt appeared to be disengaging from former associates in ALM (banned organisation Al-Muhajiroun). His focus seemed to be moving towards overseas travel, including potentially to Syria to fight with Daesh (ISIS).'

'On 21 March 2017, prior to the Westminster attack on the following day, investigation of Khuram Butt was suspended. Investigation of the other SOIs (subjects of interest) investigated under the operation had been suspended the previous week due to resourcing constraints brought on by a large number of P1 (high priority) investigations.'

The report says material relating to Butt received in the two weeks prior to the attack added little to the intelligence picture and did not identify activity that led up to the attack.

London Bridge attacker Khuram Butt had been hiding in plain sight, even appearing on TV documentary The Jihadi Next Door. He is pictured, third from the left, in the back row

Another of the London Bridge gang, Youssef Zaghba, was placed on an EU warning list in March last year.

However, Italian authorities placed him on the database under a marker identifying him as being subject to checks for serious crime rather than one which would have led to him being automatically identified as a national security risk.

It was also revealed that, in June 2016, MI5 received an inquiry from Italian authorities about Zaghba but the agency has no record of responding - 'noting by way of possible explanation that it arrived in the incorrect mailbox'.

The request was not chased up by Italian officials.

'The story is not a happy one, but, as MI5 points out, even if the request had been actioned, it would have resulted in a nil return,' the report adds.

Zaghba, and the third London Bridge attacker, Rachid Redouane, were never investigated by MI5.

Police take Khalid Masood to the ground after he drove into pedestrians on Westminster Bridge then stabbed a police officer in the grounds of the Houses of Parliament. The review found he had visited the area a week before the carry out reconnaissance

A van which ploughed into worshippers near Finsbury Park mosque in an attack which killed one. Today's report states: 'In regards to Finsbury Park, neither MI5 nor the police had any intelligence about this attack.'

Manchester attack survivor backs finding no one is to blame Steve Milward‏ survived the attack but said he is keen not to blame police and secret services for not stopping Abedi. He said in a Twitter message to the report's author David Anderson QC: 'David, as a victim of the Manchester attack, thank you for conducting a thorough review of the Police and MI5 reports and information. 'Hindsight is a wonderful thing and we must learn and move on, as you state with systemic improvements rather than apportion blame. Thank you'. Mr Anderson responded to say: 'Steve, it seems a public place to say this, but please accept my condolences on your loss, and many thanks for your kind words which mean a lot'. Advertisement

Outlining the review findings, Home Secretary Amber Rudd told the Commons: 'Based on the MI5 and police reviews, David Anderson explains that in the case of the Westminster attack, Khalid Masood was a closed subject of interest at the time of the attack.

'Neither MI5 nor the police had any reason to anticipate the attack.

'Regarding the Manchester Arena attack, Salman Abedi was also a closed subject of interest at the time of the attack, and so not under active investigation.

'In early 2017, MI5 nonetheless received intelligence on him, which was assessed as not being related to terrorism. In retrospect, the intelligence can be seen to be highly relevant.

'Had an investigation been reopened at the time, it cannot be known whether Abedi's plans could have been stopped. MI5 assess that it would have been unlikely.

'Across the attacks, including Manchester Arena, David Anderson notes that MI5 and CT policing got a great deal right.

'However, in relation to Manchester, he also commented that, quote, 'it is conceivable that the attack might have been averted had the cards fallen differently'.'

Home Secretary Amber Rudd told the House of Commons MI5 had not find any key moments where the attacks could have been stopped

Ms Rudd went on to say: 'In the case of London Bridge, Khuram Butt was an active subject of interest who had been under investigation since mid-2015.

'A number of different investigative means were deployed against him, but they did not reveal his plans.

'His two conspirators had never been investigated by MI5 or CT policing.

'In regards to Finsbury Park, neither MI5 nor the police had any intelligence about this attack.

'Taken as a whole, MI5 and CT policing conclude they could not, quote, 'find any key moments where different decisions would have made it likely that they could have stopped any of the attacks'.'

Westminster, 5 dead: The career criminal Muslim convert who changed name after prison stretch Khalid Masood, 52, killed five people and injured nearly 50 when he drove a hired 4x4 along the pavement of Westminster Bridge before stabbing a policeman outside Parliament. Masood (right) was a low level criminal who racked up a number of convictions while growing up in Kent and Sussex. But he changed his name from Adrian Ajao to Masood and was rarely seen by his family after a 2003 prison sentence for a violent attack. Instead he moved into an area of Luton known for its extremism and was alleged listed as a contact for a website which slammed Christians and Jews urged 'war' against 'the enemy of Allah'. It emerged today he was known to police and MI5 for association with extremists. But he was a closed subject of interest at the time of the atrocity in March, and intelligence officers and police had no reason to anticipate his murderous actions, according to the report. It also reveals how in the days prior to the attack, Masood conducted reconnaissance of Westminster Bridge in person and online, and browsed YouTube for videos relating to terrorism. Minutes before he struck, the terrorist shared a 'Jihad document' with numerous WhatsApp contacts. Advertisement

Manchester, 22 dead: Warning signs over suicide bomber who spent time in Libya before attack Flagged up: Salman Abedi Salman Abedi killed 22 including children as young as eight when he detonated a suicide bomb at the exit of an Ariana Grande concert in May. The 22-year-old British-born son of Libyan immigrants to the UK, Abedi (right) was on MI5's radar after security services were alerted to his extremist views. Today's report revealed security services were passed two pieces of information on the bomber earlier this year. The report said security services did not consider the intelligence terror-related at the time, but now says it was 'highly relevant'. 'It is conceivable that the Manchester attack in particular might have been averted had the cards fallen differently,' the report said. He had travelled to extremism-plagued Libya and Istanbul shortly before the attack and authorities have said he did not act alone. UK prosecutors are currently trying to negotiate the extradition of his brother Hassem, who was arrested in Libya after the attack having previously been pictured online brandishing a machine gun. Advertisement

London Bridge, 8 dead: TV jihadi, failed asylum seeker and 'red flag' Italian behind van and knife attack The ringleader of the London Bridge terror gang was the subject of a two-year MI5 investigation prior to the atrocity, the report reveals. Khuram Butt was the subject of various kinds of 'coverage' from the middle of 2015 following information suggesting he aspired to carry out an attack in the UK. The assessment of intelligence handling published on Tuesday said: 'Though it continued to varying degrees until the day of the attack, it did not reveal the plans of Khuram Butt and his two co-conspirators.' On June 3 a van ploughed into people on London Bridge before 27-year-old Butt, Moroccan Rachid Redouane, 30, and 22-year old Italian/Moroccan Youssef Zaghba launched a knife rampage around Borough Market. Eight victims were killed, while the perpetrators were shot dead by police. Butt was the only terrorist involved in the four attacks examined in the review who was a live 'subject of interest' and under active investigation at the time of the attack. Failed asylum seeker Rachid Redouane (left) and extremist Youssef Zaghba (right) Born in Pakistan in 1990, his family moved to England in 1998, claiming asylum before being given indefinite leave to remain in 2004. Butt was given British citizenship in 2005. In January 2016 Butt, who had no criminal convictions, was identified posing with an Islamic State flag in the Channel 4 television documentary The Jihadis Next Door. While under investigation by MI5, Butt was arrested for fraud in October 2016 and granted bail. Two days before the attack, a decision was made not to prosecute him. Moroccan Redouane had been refused asylum in 2009, when he was using the name Rachid Elkhdar, yet managed to stay in Britain after marrying an Irish woman in Dublin. CCTV showed the moment armed police arrived at the scene and killed the trio He had previously been arrested in Scotland attempting to travel to Northern Ireland by ferry on a fake passport. Moroccan-born Italian Youssef Zaghba meanwhile to the Italian authorities in March 2016 when he tried to fly from Bologna to Syria via Istanbul. His name was put on The Schengen Information System - a red flag warning system informing other European nations if criminals are trying to enter their country. Yet British border guards did not stop him entering the UK at least twice. Advertisement

Finsbury Park, one dead: Attack suspect 'was seen by police in van' A Londoner leaves flowers at the site where a man was killed and 11 injured On Monday, 19 June a man in a hired van mounted the pavement outside the Muslim Welfare House in Finsbury Park. The centre is down the road from the Finsbury Park Mosque, which previously had problems with extremism but has since worked to tackle the issue. The area was busy with Muslim worshippers attending Ramadan night prayers at the time. One man, 51-year-old Makram Ali, died from his injuries after the attack and 11 others were injured. It was claimed after the attack that police had seen the suspect asleep and drunk in the vehicle 24 hours before the attack, but took no action. Today's report found neither police nor MI5 had any information about the attack or any suspects before it was carried out. Advertisement

Calls for more funding and better technology as terrorist threat continues to grow

Shadow home secretary Diane Abbott has warned ministers they 'cannot keep people safe on the cheap' as stretched security services failed to stop the Manchester suicide bomber.

The head of Scotland Yard Cressida Dick also called for more cash to fight terror to pay for new technology, better infrastructure and staff.

Ms Abbott spoke out as an independent terror assessment noted a reduction of 7.2% in grant funding over the next three years.

Home Secretary Amber Rudd hit back at the suggestion, saying the Government was ensuring the UK was 'always properly resourced on this subject'.

Shadow Home Secretary Diane Abbott criticised the government over police funding

Ms Abbott said: 'The Home Secretary concedes that linked to the implementation of review recommendations are resources - as we say on this side of the House, you cannot keep people safe on the cheap.

'She will shortly be announcing the budgets for policing in 2017/18; she talks about ensuring that counter-terrorism policing has the resources it needs.

'But does she expect the part in David Anderson's report where he notes that the counter-terrorism indicative profile of their grant allocation over the next three years sees a reduction of 7.2% in their budgets?

Met Police Commissioner called for 'rapid progress' in bringing in new technology

'Does she agree with David Anderson when he talks about the reliance of MI5 and counter-terrorism on community policing? Does she accept that proper funding for community policing is at least as important as resources for counter- terrorism proper?'

Ms Rudd responded: 'I would not want her to imply that the report covers any suggestion that these attacks wouldn't have taken place if there was more resourcing.

'It's fine to ask about more resourcing, and I have acknowledged that there's going to be a need for more, but I would also point out that in 2015 the Government recognised the need for more resourcing and put an increase from £11.7 to £15.1 billion over 2015 to 2020 into the CT budgets to ensure that this country, through this Government, is always properly resourced in this subject.'

Speaking outside Parliament, Manchester's mayor and former shadow home secretary Andy Burnham said the report 'would be difficult reading for everyone in Manchester' and called for more funding to local police to tackle the terror threat.

Mr Burnham said: 'I accept [the report's] conclusion that there's no way of knowing whether the Manchester attack could have been stopped, but it's clear that things could and perhaps should have been done differently and also that wrong judgments have been made.'

Manchester mayor Andy Burnham, pictured at the funeral of the youngest Manchester bombing victim, eight-year-old Saffie-Rose Roussos, said the report was 'difficult reading'

He welcomed the report's call for two-way intelligence sharing between national counter-terrorism units and local police forces and urged the government to increase funding to Greater Manchester Police.

'Real-term cuts to the police budget must stop and increases are given to reflect the greater work load and the growing threat,' he said.

Mr Burnham praised security services, saying: 'It's right and important to note that the authorities got a lot right in respect of the Manchester Attack.

'The fact that they were closing in on the perpetrator should reassure the public of the professionalism of our police and security services and the systems that they use. It would be much more worrying if nothing had been known about the attacker.'

But he added: 'Clearly systems can be improved further still.'

Director General of MI5 Andrew Parker said his agency would learn from the report

Met Commissioner Cressida Dick said: 'We need to make rapid progress in implementing the recommendations, many of which require new technology, better infrastructures and resources at a time when the threat from terrorism poses significant challenges for police and security services.

'The growth in the number of dangerous individuals who have been radicalised is a major issue for us.

'We will be redoubling our efforts in enforcement activity both to disrupt and confront the threat and to safeguard the vulnerable from radicalisation.'

In its full response to the report released on Tuesday, the Met said the 'tempo' of activity being confronted by counter-terror agencies is 'more intense than ever'.

The force said: 'Although we work tirelessly to keep the country safe the reality of the terrorist threat means that we will not stop every attack.'

Andrew Parker, the Director General of MI5, said the agency is committed to implementing the recommendations identified in the report.

He added: 'We and our partner agencies used the harsh light of hindsight under independent challenge to ensure we squeezed every drop of learning out of these dreadful events.

'MI5 and our partners continue to bring the full weight of our growing capabilities to counter this new intensity of threat.

'Our unrelenting focus remains on doing everything in our power every day to keep the country safe.'