Your instincts are better than you think. Here's why that matters.

What would you do if you saw something that didn't feel right? Not a weapon, not an obvious threat, just something. A person, a behaviour, a detail that made the back of your neck prickle and left you with a feeling you couldn't quite name before your brain had caught up with why.

Would you say something, or would you talk yourself out of it, worry about being wrong, about causing a scene, about wasting someone’s time? Most of us glance across, decide it’s probably nothing, and look back at our phones.

Most people did exactly that on 22 May 2017 at the Ariana Grande concert in Manchester Arena. One person didn’t. They noticed Salman Abedi, they were concerned about what they saw, and they told a security steward. That night, 22 people died.

I work in security and I have spent a significant part of my career thinking about exactly this kind of gap, the space between something being preventable and something becoming irreversible. What the Manchester Arena Inquiry revealed is that the warnings were there, the behaviours were visible, and the systems that should have caught them fell short in ways that were entirely avoidable.

People who act on gut-based instincts are significantly more certain of what they have seen and considerably more willing to speak up about it.1

There is real science behind that feeling, and it is worth understanding. Research co-authored by academics at Yale University and published by the American Psychological Association found that gut-based decisions feel like a more accurate reflection of what we genuinely know. Understanding that is the first step toward doing something useful with them.2

Salman Abedi didn't arrive on the night of 22 May and improvise. He had been planning for months, and in the days immediately before the attack he did something that anyone trained in security would recognise: he carried out hostile reconnaissance.3

Hostile reconnaissance is exactly what it sounds like. Before an attack, a perpetrator visits the target and studies it carefully, looking for entrance and exit routes, identifying where security is strongest and where it falls short, locating cameras and finding the blind spots, working out where to be, when to be there, and what they can get away with. It is methodical and patient, and to the untrained eye it looks like someone simply hanging around.

Abedi made three confirmed visits to the Arena in the days before the attack, the first on 18 May during a Take That concert, four days before the bombing, then again on 21 May, and on the afternoon of 22 May itself he entered the City Room briefly, spoke to two security stewards, and left.4 He came back that evening at 8:30pm carrying his rucksack, which CCTV later showed him bent under, at one point fiddling with wires visible at his clothing. He made his way to the mezzanine level of the Arena foyer - a spot he had already identified during his earlier visits as a CCTV blind spot, and waited there for 58 minutes, having already established in advance that nobody would patrol those stairs.56 At 22:31, he detonated his device.

I spent a period of my career heading up a large behavioural detection team in London, and the distinction my team worked to is one I want to be clear about, because it matters enormously. We were not profiling people.

Profiling is looking at what someone looks like. Behavioural detection is looking at what someone is doing, how they are moving, and whether their behaviour fits the environment they are in.

Every environment has a baseline. A busy train station at rush hour looks, sounds and feels a particular way, a concert venue has its own rhythm, and most people, consciously or not, fit that rhythm. They move with purpose or they browse without it, they look at things worth looking at, and their body language matches what they are doing. When someone deviates from that pattern it registers, and often it registers before you have found the words for why.

On one occasion my team reported a concern about an individual whose behaviour had taken them well outside that baseline. It was a hot day and they were wearing multiple layers with their hood up, they had lapped a couple of buildings in a way that had no natural purpose. This individual then placed their rucksack on the floor and was walking away from it, returning every thirty seconds or so to check it before moving away again. None of those things in isolation is necessarily suspicious, but together, in that context, on that day, they formed a pattern. We reported it and the individual was met by police, which is the system working exactly as it should - a trained eye, a decision to act on what was seen, and a report taken seriously, with nobody talking themselves out of it.

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The Manchester Arena Inquiry produced three volumes of findings, and the conclusions make for difficult reading, not because of their legal complexity but because of their simplicity. Two police officers who should have been on duty were on a two-hour dinner break five miles away, the mezzanine area where Abedi waited for nearly an hour was nobody’s responsibility to patrol because the venue operator and the security contractor had different understandings of whose job it was, and the CCTV operators had not detected his reconnaissance visits in the preceding days despite him walking up and down in front of the entrance doors, yards from security personnel.78 The Arena’s risk assessment was fundamentally flawed, designed in a way that could only produce a low-risk outcome for a terrorist attack, even though on 22 May 2017 the national threat level was SEVERE and an attack was considered highly likely.9

And then there is the detail that stays with me most. A member of the public noticed Abedi and was concerned about his bag, which was large and visibly heavy, and they told a security steward. The Inquiry chairman Sir John Saunders described this as the single most significant missed opportunity of the entire night, the one intervention most likely to have made a difference.10

The behaviours were there, the concern was raised, and the system around it failed to respond.

I want to be careful about how I frame what follows, because the Manchester Arena attack is not a case study in a textbook. Twenty-two people died and hundreds more were injured, many with life-changing consequences. Martyn Hett was 29, and the law carries his name because his mother, Figen Murray, refused to let his death mean nothing, and she has spent years turning the most unimaginable grief into something that might protect others from the same fate. This article exists, in part, because of her.

The reason Manchester matters beyond Manchester is that the pattern is not unique. The hostile reconnaissance, the visible warning signs, the failure to communicate, the failure to act on a concern raised by a member of the public - that gap exists, to varying degrees, in almost every public space, and it will keep existing until the people responsible for those spaces are required to close it. That is what Martyn’s Law is attempting to do.

MARTYN’S LAW — THE TERRORISM (PROTECTION OF PREMISES) ACT 2025

Martyn's Law is aimed at venues and operators, but the lesson of Manchester is not only institutional, it is human. You do not need to be a trained behavioural detection officer to trust what you already notice. You know what normal looks like in the places you spend your time, and when something deviates from that you feel it before you can explain it. That feeling is worth acting on.

Counter Terrorism Policing runs ACT, which stands for Action Counters Terrorism, and the message is a simple one: if something does not feel right, report it. Reports are reviewed around the clock by specialist teams and you will not be wasting anyone's time by raising a concern in good faith.11 For venues and their staff, SCaN (See, Check and Notify) is a free e-learning tool from Counter Terrorism Policing specifically designed to build awareness of hostile reconnaissance and how to respond to it, taking 45 minutes, costing nothing, and with genuinely no reason not to do it.12

I started this piece with a question. What would you do if you saw something that didn't feel right? I think, if you've read this far, you already know the answer. The harder question is whether you'll act on it.

Safety and Security. From someone hired to protect.

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