On the fortieth anniversary of its first broadcast in 1984, this article will consider the main themes of the BBC TV series The Sea of Faith , written and presented by the Cambridge philosopher and theologian Don Cupitt. It will attempt to evaluate its significance, then and now. We argue that Cupitt’s ‘radical’ reputation for his advancement of a broadly ‘non-realist’ understanding of God may have overshadowed other equally significant features, not least his central argument that unless Christianity responded constructively to modern thought it would be doomed to irrelevance. The article will close with some reflections on what Cupitt’s manifesto for religion might mean for those who continue to identify with his critiques of traditional theology today.