The law governing compulsory motor insurance is fundamental to the tort system and subject to considerable harmonisation. It is a vital part of the life cycle of liability and liability insurance. This chapter considers the expansive vision of compulsory insurance as a guarantor of compensation to third parties under European Union (EU) law alongside the subtle and not so subtle resistance evident in the English courts. The need to identify the proper limits on insurer liability to victims of motor accidents is made more pressing by Brexit. United Kingdom law will have to decide – and soon – whether to voluntarily follow EU standards on third-party protection or endanger cross-border travel and trade.