This article argues that British historiography's secularization debate is largely misconceived, being enmeshed in secular ideological assumptions inherited from the West's secular revolution of the 1960s. It therefore introduces an alternative, postsecular paradigm for understanding British secularization, which conceptualizes secularity as an ideological culture in its own right, religion as secularity's othering category, and secularization as the positive dissemination and enactment of secularity. British Christianity declined gradually from around 1900, but widespread secularization in this positive sense could only happen once British public discussion had embraced secularity's ideological framework, which it did in the late 1950s and early 1960s. Before the mid-1950s, British discussion had routinely adhered to a “Christian civilization” metanarrative, which insisted that “religion” is essential to long-term social stability, such that “secularization” is a regrettable step backward in human development. Yet in the late 1950s and early 1960s British discussion abruptly embraced secularity's rival metanarrative, which states that “religion” is a primordial condition unnecessary in “advanced” societies, such that “secularization” is an irreversible step forward in human development. This conceptual revolution was contingent, culturally specific, and importantly influenced by radical rereadings of Christian eschatology. Nonetheless, it created both the secular revolution of the 1960s, and the ideological framework within which the British secularization debate continues to be conducted today.