This thesis is an ethnographic investigation into how Pentecostalism impacts on the religious, family and work life of Nigerian migrants in London, and overall how such religious engagement shapes informants' relationship with the United Kingdom. It brings together the study of migration, Pentecostal Christianity and gender relations. The thesis focuses on the members of the Redeemed Christian Church of God (RCCG). The RCCG is one of the biggest Pentecostal churches in Nigeria, where it has developed into a significant social and political player and has spread worldwide. In London, the RCCG caters for a good portion of the local Nigerian Christian community. The RCCG is part of a transnational social and moral field that I term 'London-Lagos', which Nigerian migrants inhabit. RCCG members' relationships in church, with significant others and with wider society are embedded in power relations - relations that are mediated and rendered meaningful by a Pentecostal morality. The negotiation of moral authority is therefore central theme in this thesis. I trace how it shapes and is shaped by church doctrines and wider British society. The central modes employed to mould Pentecostal Nigerian selves in London are self-discipline, the dialectic of submission and responsibility, and the disciplining of others. Such dynamics around Pentecostal authority are crucially articulated in gendered terms. Hence, they are investigated in relation to gendering processes in singlehood, marriage and the raising of children. The requirements of non-Pentecostal contexts such as wider British society and state institutions sometimes contradict this three-fold way of becoming a morally sound Pentecostal. To navigate this tense and morally complex situation RCCG members tend to employ skills ('smartness') they have obtained in Nigeria.