Video report by ITV News correspondent Rebecca Barry
Potential opportunities to prevent the Manchester Arena attack were missed due to a catalogue of failures in dealing with bomber Salman Abedi, a report into the five terror attacks the UK suffered in 2017 has found.
However, the report by the Intelligence and Security Committee entitled The 2017 attacks: What needs to change? said that it was "impossible" to say whether these failures could have "prevented the devastating attack" which killed 22 people.
Along with Manchester, the Parliamentary committee examined the Westminster Bridge, London Bridge, Finsbury Park and Parsons Green attacks in a bid to determine if mistakes were made which enabled the attacks to happen, and understand what could be learnt from them and what improvements should be made.
The five attacks left a total of 36 people dead and hundreds more injured.
As well as the Manchester attack, the committee said there appeared to have been "fundamental failings" in the way police and the Home Office handled Parsons Green attacker Ahmed Hassan.
However, due to an "unacceptable" delay by the Home Office in submitting information on the incident, the attack was not included in the final report, with a separate one commissioned for the future.
In the case of the Manchester Arena attack, the report's authors found the following failures by authorities when dealing with Salman Abedi:
The 22-year-old visited an extremist contact in prison on more than one occasion, however no follow up action was taken by either MI5 or counter terrorism police.
MI5 decided not to place travel monitoring or travel restrictions on Abedi which allowed him to return undetected to the UK from his home country of Libya in the days immediately before he carried out his attack.
Abedi was not considered for a referral to the Prevent programme which seeks to counter extremism.
Abedi had been flagged for review, but MI5's systems moved too slowly, highlighting deficiencies in the organisation's system for monitoring individuals of interests not currently under investigation.
A further issue was raised but could not be reported on due to highly sensitive security aspects.
Following the findings of these failures, the committee - which has oversight of the UK intelligence community - recommended that the Approved Visitors Scheme (where photographs and details are taken of people visiting inmates of Category A prisons) should be extended to all extremist prisoners.
The report also states that policies on travel monitoring and restrictions should be revised.
It goes on to recommend improvements in the monitoring of individuals of interest not currently under active investigation, and states that failure to use Prevent is "not a new issue and we would have expected lessons to have already been learned".
In relation to the three other attacks (excluding Parsons Green), the authors of the report found that the system for regulating and reporting the purchases of the ingredients used to make explosives was hopelessly out of date, thus facilitating the perpetrators.
The report states that more must be done to improve co-operation and information sharing between retailers and law enforcement.
It also criticised internet companies, saying they do not do enough to stop their systems being used as safe havens for extremists and terrorists to communicate.
The authors said the Government should be tougher on Communications Service Providers by targeting their profits and encourage advertisers to put pressure on them, both of which it believes would "hit home harder" than appealing to them to "do the right thing".
The committee criticised authorities for not having learnt and acted enough from past terror attacks in the UK, such as the 7/7 bombing and the killing of Lee Rigby.
"We have previously made recommendations in all of these areas," the authors said, "yet the Government failed to act on them".
The report concludes that while both MI5 and counter terror police "have been thorough in their desire to learn from past mistakes", the lessons from last year's tragic events must now result in real action.
Currently in the UK there are more than 700 live counter terrorism investigations involving some 3,000 individuals who are believed to pose the biggest threats, while another 20,000 people are classed as individuals of concern.
Manchester Arena victim, Martin Hibbert, said he hoped that the report would make "people sit up and do something".
Mr Hibbert, who was the closest person to the bomber to have survived, told ITV News: "We need our M15 and counter-terrorism units to step up. But also we need the government to give them money to do that.
"We need more police officers, we need more cash. So if prime minister Theresa May's watching, when you do the review next year, these guys need cash. to protect individuals like me."
In response to the report, Neil Basu the National Head of Counter Terrorism Policing said the body was "grateful for the depth and breadth of this review.
"We will now look in detail at the full report, which we will need to take time to consider carefully.
"There will be further scrutiny and examination into the circumstances of these attacks, including coronial inquests and other potential criminal proceedings, which may preclude us for the time being from commenting publicly to some specific points raised.
"In the meantime we would like to reassure the public that ever since the attacks of last year we have sought to learn from what happened before, during and afterwards, and improve our wider operating model and ways of managing and mitigating the risk from terrorism...
"Working evermore closely with the Security Service and learning our lessons, we will do everything we can to reduce the chances of this happening again."
The Assistant Commissioner of the Metropolitan Police said these improvements would include piloting multi-agency centres to share intelligence, improving intelligence handling and assessment, and the better use of data.
Home Secretary Sajid Javid added: "My thoughts remain with the victims and families of last year's attacks - which only serve to strengthen our resolve against those who seek to threaten our freedoms and do us harm...
"We have updated our counter-terrorism strategy, introduced new legislation to allow threats to be disrupted earlier and have increased information-sharing with local authorities.
"We are also ensuring technology companies play their part by stopping terrorists from exploiting their platforms."