Every police officer knows they must have a reasonable suspicion that a person has committed an offence in order to arrest them. But that is only half of what is required. The second element is that they must have a reasonable belief in the necessity for the person’s arrest. The recent decision of Commissioner of the Metropolitan Police v MR [2019] EWHC 888 (QB) is one of a number of recent cases where appellate judgments have sought to tighten-up what the police must show in order to prove necessity.

In the instant case, a woman ‘A’ and her partner ‘MR’ had been in a relationship for fifteen months. A complained to the police about MR, who could not be traced save for a mobile telephone number. A police officer called MR on 11 January 2010, who then attended a police station for voluntary interview on 12 January 2010. Whilst at the police station and before being interviewed, MR was arrested on suspicion of harassment. He was interviewed, photographed, and had his fingerprints and DNA samples taken. After nearly seven hours, the police released him on conditional bail. He claimed that the arrest and consequent detention was unlawful and was subsequently successful in the county-court. The Comissioner appealed to the High Court.