In R (Rose) v Chief Constable of Greater Manchester Police [2021] EWHC 875 (Admin), a businessman successfully challenged a decision not to refer his complaint to the Independent Office of Police Conduct (IOPC) under the mandatory referral criteria. The High Court concluded that the chief constable had failed to review the conduct alleged and consider whether, if substantiated, it would constitute serious corruption as defined in the (then) Independent Complaints Commission (IPCC) Statutory Guidance on the handling of complaints. Instead, he had performed an assessment of the merits which had rendered the decision not to refer the complaint unlawful. The case makes clear that complaints engaging the mandatory criteria, especially that of “serious corruption”, must be referred to the IOPC.