Résumé : On January 31st, 2020, the United Kingdom withdrew from the European Union, and their mutual relationship entered in a phase of transition. After 47 years of membership, the withdrawal led to a series of changes in various policy areas, in which the UK, as an EU Member State, cooperated with its counterparts. This notably concerns police and judicial cooperation in criminal matters, and the consequences of Brexit in this particular field will be our focus.Police and judicial cooperation in criminal matters is not necessarily the most discussed areas of mutual cooperation between EU Member States. Yet the instruments elaborated in this field are often relied upon in the background of highly visible cases, among which the emission of European arrest warrants (EAWs) against Catalan politicians, like Carlos Puigdemont, or the creation of a joint investigation team between France and Belgium after the Paris attacks in November 2015. These instruments are also frequently relied upon by British authorities, such as in the course of the investigations that were launched after the macabre discovery of 39 bodies in the “Essex Lorry”. The investigators retraced its movement from Bulgaria to the UK, through Belgium, notably with the assistance of one of the EU specialized agencies, Europol, and EAWs were issued against a person residing in Ireland suspected to have been involved in the criminal operation.