In the first episode of ITV’s Worlds Collide: The Manchester Arena explores the events that led to Salman Abedi’s radicalisation and the opportunities that were missed to stop his plans.

The film documents how intelligence agencies missed multiple links between Abedi and terrorist activity. M15 had previously flagged him as a threat and he was well known to be “on the edges of bad stuff that was going on” as part of groups in south Manchester with ties to ISIS.

Interview footage from the Manchester Arena Enquiry hearings showed members of the British Transport Police (BTP) and Manchester Arena stewards who encountered Abedi moments before he detonated the bomb being quizzed on whether they could have done more to prevent the attack.

“If he had walked past me, I probably would have asked him what was in his backpack,” one BTP officer, who had ignored orders to be visible and took a two-hour break as Abedi boarded the train towards the arena, admitted.

An arena steward told the inquiry that he had encountered Abedi just minutes before the attack and found him “suspicious”, but was “scared of being wrong and being branded a racist”.

Worlds Collide: a harrowing new ITV documentary investigates the truth about the Manchester bombing five years on