The religious beliefs of the Jewish and Irish communities in East London played a key role in demarcating their differences from wider mainstream British society. It was religious faith that helped cement a diasporic identity that crossed class and national boundaries. Religious institutions also provided a ready-made structure of communal leadership for migrant communities. The durability of minority religious observance was noted by contemporary observers, as compared with a largely non-religious wider working-class culture. However, there were negative as well as positive ramifications for the strength of faith amongst the Irish Catholic and Jewish communities, as far as the diasporic groups were perceived in the wider society. The way in which religion cut across class and national lines, as well as its seemingly alien elements, with unfamiliar rituals and prayers recited in a foreign language, could lead to accusations of conspiracy and suggestions of hidden transnational ecclesiastical networks by both the political right and the left. For H.M. Hyndman, the supranational element of ecclesiastical commitment smacked of reactionary conspiracy, whilst for Beatrice Webb and Robert Blatchford, the strength of Jewish and Catholic religious loyalty caused ideological difficulties. Other socialists, such as the now obscure one-time Catholic Fabian Robert Dell, spent a part of their political careers attempting to reconcile socialist politics and minority religion.

For both the Irish Catholic and Jewish diasporas transnational belonging and identity were a complex composite mixture of both religious and ethnic loyalties and roles. These roles, and identification with a wider minority community, were not set in stone, but were conditional and often changing. For the BoD, the United Synagogue, and the Beth Din in the 1890s, involvement by a Jewish socialist or trade unionist in ‘extreme’ left-wing political activity could effectively negate the Jewish identity of the offender. Similarly, a failure, particularly by certain radical members of the clergy, to follow the strictures of the Church, or to fall into such ‘deviations’ as Modernism, could potentially forfeit Catholic belonging not only in this world but in the next. The Church had the ultimate sanction of excommunication and the withholding of religious rites at the individual's funeral and burial were the potential consequences of political or spiritual ‘deviation’.