MI5 bosses failed to act on two separate warnings that the Manchester Arena bomber was buying bomb-making ingredients in the months before the attack.
The Mail on Sunday has learned that the agency received two ‘pieces of intelligence’ about the purchase of chemicals by Salman Abedi and his associates, but failed to realize the ‘importance’ of the information.
Sir John Saunders, the chairman of the inquiry, revealed in his final report that a delay in reporting the second piece of intelligence within MI5 and to the police resulted in a “significant missed opportunity to take action that could have prevented the attack”.
But a source dealing with national security issues has told how the two pieces of information related to Abedi, 22, and his associates were buying ‘chemical precursors’ used to make an explosive substance called triacetone triperoxide (TATP), dubbed mother of satan .
It was this substance that was in the deadly bomb that killed 22 victims, half of whom were children, at the end of an Ariana Grande concert on May 22, 2017.
The Mail on Sunday has learned that the agency received two ‘intelligence pieces’ about Salman Abedi’s purchase of chemicals (pictured)
It is not clear why the information was mishandled.
Relatives of the victims reacted angrily last night. Andrew Roussos, whose eight-year-old daughter Saffie-Rose was the youngest victim of the atrocity, said: “This information is key to understanding the scale of intelligence failures.”
Roussos and at least 15 other families have previously spoken of their plans to sue MI5 for negligence. The Manchester Arena inquiry was highly critical of MI5, accusing it of being responsible for an intelligence “failure” in the run-up to the attack.
It was these damning conclusions that led Ken McCallum, the Director General of MI5, to issue a rare public apology to the families of the victims. In November 2021, Sir John held closed-door evidentiary hearings that the media were unable to report.
During a ten-day session, Sir John heard testimony from five MI5 officers, including those who actually handled and evaluated the two pieces of intelligence.
In his report, Sir John said that Witness J, speaking on behalf of the Service, said that the two pieces of intelligence were deemed not to be related to terrorism.
But MI5 officers, Witnesses A, B and C, told the inquest they believed the second piece of intelligence, when considered alongside the first, could be of “pressing national security concern”.
However, despite this, the investigation found that the two pieces of intelligence were not acted on quickly enough or shared with counter-terrorism police. Meanwhile, MI5’s own internal report was delayed and did not provide enough context for other officers to understand its full meaning.

Andrew Roussos, whose eight-year-old daughter, Saffie-Rose (pictured), was the youngest victim of the atrocity, said: “This information is key to understanding the scale of intelligence failures.”
If MI5 acted on their intelligence, Sir John concluded, then Abedi could have been stopped and searched at Manchester airport four days before the attack while returning from a trip to Libya.
The investigation also found that he could have been followed afterwards, which could have led MI5 to a Nissan Micra that was used to store the homemade explosives.
Abedi and his younger brother, Hashem, 26, who is now serving a life sentence, persuaded two cousins and a friend to buy them sulfuric acid from Amazon.
At Hashem Abedi’s trial at the Old Bailey, he was heard to have told his two cousins, who were cleared by police of any wrongdoing, that the acid was to recharge a car battery. But it was actually one of the necessary ingredients for the bomb.
Then followed the purchase of hydrogen peroxide, the main ingredient in TATP, through fake Amazon accounts. MI5 had claimed officers analyzing the intelligence took it as “criminal activity” related to “drugs or organized crime”.
Hydrogen peroxide can be used for hydroponics, the process used to grow cannabis plants in water, and Salman and Hashem Abedi had been drug users in the past.
But the chemical was also the main ingredient in the suicide bombs used in the London Transport bombings of July 7, 2005.
Last night, a Home Office spokesman, speaking on behalf of MI5, said: “The President (Sir John) has published his findings and the Government will not engage in speculation about them.”