This article extends and develops recent historical discussion on the relationship between British Christianity, sexuality, and modernity, proposing some ways forward for future scholarship. Recent accounts have concentrated on liberal Anglican positions on issues of sexuality, but here the focus is on the British Council of Churches, its early moral welfare work, and interdenominational efforts to reconsider Christian sex teaching in the immediate post‐war years. While examining broader trends towards positive statements about sex and attempts to assemble self‐regulating sexual citizens in Christian moral welfare thinking, the article suggests that, far from a narrative of relatively untroubled and gradual acceptance of progressive Christian views on sex, this was a halting and uncertain process. The article reflects closely on the complexities of post‐war Christian attempts to work with new ideas about sexuality and to formulate their own version of them, the difficulties and ambiguities involved in developing a cogent position in a debate where Christian opinion was so fiercely divided, as well as the complicated nature of institutional decision‐making. As a case study, the British Council of Churches reflects earlier, problematic attempts to alter Christian sex teaching, as well as the unfolding of later difficulties for the British churches.