Materials Detectives was a workshop for Year 12 pupils, funded by the Queen Mary Centre for Public Engagement and delivered at Queen Mary on 28 February 2026 with SEMS Recruitment and Marketing. Pupils worked through realistic materials-engineering "cases": a dataset in which the cause of a problem is hidden among many plausible factors and released progressively as clues, so that forming, testing and revising hypotheses becomes the activity itself rather than something to get right first time. The format, a three-phase "detective" framework for developing reasoning within a single session, was designed for Year 3 undergraduates on the QMES programme; the workshop tested whether it transfers to pre-university learners, and asked pupils to explore where AI tools help with an engineering problem. Twenty-six pupils from eleven schools took part, supported by three student ambassadors, and the workshop data form the outreach arm of a research paper now available as a preprint.