Opportunistic insurance fraud occurs when otherwise law-abiding citizens submit false or exaggerated information during insurance application or claim processes to get a better deal for themselves. Estimated to cost the industry up to £1B a ye approach, we simulated real-world motor insurance application and claim processes on over 12,000 motor insurance customers. In combination with innovative surveying techniques such as the Unmatched Count Technique (UCT), we sought to understand the true extent of dishonesty and the impact of interventions in reducing it. The results were staggering, with interventions having an average effect of a 36% dishonesty reduction. Top performing interventions, and using multiple interventions simultaneously, further boosted the effect size to above 70%. We believe this work deserves this award as these results have enormous implications for the industry and its customers, with potential annual savings amounting to £260m.