Political protestantism has been an enduring theme in parliamentary and ecclesiastical politics and has had considerable influence on modern Church and state relations. Since the mid 19th century, evangelicals have sought to apply external and internal pressure on parliament to maintain the ‘protestant identity’ of the national Church, and as late as 1928, the house of commons rejected anglican proposals for the revision of the prayer book. This article examines the attempts by evangelicals to prevent the passage through parliament of controversial measures relating to canon law revision in 1963–4. It assesses the interaction between Church and legislature, the influence of both evangelical lobbyists and MPs, and the terms in which issues relating to religion and national identity were debated in parliament. It shows that while evangelicals were able to stir up a surprising level of controversy over canon law revision – enough for the Conservative Party chief whip, Selwyn Lloyd, to attempt to persuade Archbishop Ramsey to delay introducing the vesture of ministers measure to parliament until after the 1964 general election – the influence of political protestantism, and thus a significant long-term theme in British politics, had finally run its course.