Abyei was one of the most contested areas of Sudan’s Comprehensive Peace Agreement (CPA) of January 2005. Drawing on direct experience, the article examines the agreement and the experience of trying to support its implementation. It analyses the relationship between this and the overall problems of the CPA, and of peacekeeping in the newly independent South Sudan. Drawing on relevant literature, it examines the wider issues for the negotiation of peace agreements; for UN mandates,…