Manchester Arena Bombing (2017)

The Manchester Arena Bombing remains the deadliest terrorist attack at a UK concert venue, with 22 fatalities including children. The inquiry found that security staff had identified bomber Salman Abedi as suspicious 15 minutes before the detonation but failed to intercept him—a critical 56-second window for intervention after his final behavior change. This lapse surpasses even #4 Hillsborough's police failures in its preventable nature, as Abedi was known to intelligence services. Over 800 people were injured or psychologically scarred, and the subsequent review mandated venue security reforms costing £12 million industry-wide.