A tribunal examining the Manchester Arena bombing is hearing claims of ‘institutional defensiveness’ from MI5 and other security services in the wake of the 2017 attack. During the proceedings, it was revealed that the security services allegedly failed to acknowledge critical mistakes that may have prevented the tragedy. Legal representatives for the victims argue that MI5’s responses lacked transparency, while MI5 asserts it acted with candor. With over 250 claimants, including bereaved families, the case highlights key issues regarding intelligence handling and accountability within UK security operations.