The UK government's consideration of whether to replace Trident evokes past controversies about the bomb including occasions when the Labour Party advocated unilateral renunciation of British nuclear weapons. Out of office, fierce debate engulfed the party, fuelled by, and in turn fuelling, intra-party conflict. In power, while Labour governments took different decisions on key defence issues to their Conservative counterparts, they nevertheless ensured that the UK remained a nuclear weapons state. Labour also ensured the habits of secrecy in nuclear decision-making were ingrained, though these were challenged by the current government. This article examines the development of Labour's approach to nuclear weapons since 1945. Particular attention is given to the 1980s as members of the current cabinet will have clear recollections of campaigning on an anti-nuclear policy in the 1980s. The Blair government has embarked on public debate ahead of a formal decision and should the issue of Britain's nuclear status become embroiled in a political battle over the leadership succession, anti-nuclear sentiment may re-emerge. Yet if the past is guide to the future, the history of Labour governments suggests that the real debate will be about what replaces Trident not whether it is replaced.