Taking the moment of imminent UK exit from the European Union as an opportunity to reflect on the mutual influence of the CJEU and the English courts, this chapter examines 113 preliminary references made by the higher English courts over a 10-year period to investigate two related questions. These are: first, the extent to which the CJEU’s rulings have been implemented by the British courts, and second the extent to which the interpretations proposed by the UK courts seem to have influenced the CJEU. On the first question, the study finds that there is a remarkable lack of information available about what happens following preliminary rulings of the Luxembourg Court, which makes it very difficult to assess the extent to which the preliminary rulings of the CJEU were implemented by the referring UK courts in this study. On the second question, the findings of the study suggest that in the substantial number of cases in which the British courts advanced a proposed interpretation of EU law, the CJEU adopted that interpretation in a majority of those cases. Hence, even though the CJEU has rarely acknowledged the influence of national referring courts on its rulings, the cases referred from the higher UK courts over the past decade suggest that instead of a one-way relationship in which British courts were subject to the overriding authority of the CJEU, there was arguably a process of mutual influence in which the Luxembourg court more often than not adopted the interpretation of EU law proposed by the British court.