The Irish in Britain are paradoxically Britain's longest established major ethnic group and also its least researched British sociologists influenced by the race relations paradigm that has dominated ethnic research have ignored the Caucasian, English language speaking, Irish in Britain; dismissing them as having no specific ethnic linked problems. This thesis strongly argues however that the Irish in Britain do have ethnic linked problems; essentially stemming from the nature of the political relationship between Britain and Ireland. This thesis locates the 'uniqueness' of the Irish in Britain historical experience in this bipolar relationship and in particular the anti-colonial struggle which resulted in Southern Ireland being the first British colony to win its political independence by military means in this century. Very few other British colonies repeated this experience and only in the Irish case did the colonial violence spill over into the metropolitan country in the form of organized 'second front' operations. Every generation of Irish immigrants in the last 120 years has seen some of its members participating in these activities; generating widespread macro societal hostility. This thesis focuses on the particularly traumatic 1916-23 period. It makes a substantial contribution to the little explored political sociology of non-electoral participant organizations by its detailed investigation of the Irish Self Determination League: the largest ethnic political organization to emerge in England and Wales. This thesis also breaks new ground in evaluating the contribution made by the IRA units in Britain towards winning political independence for Southern Ireland. This thesis also compares the response of the Irish in Britain to the anti-colonial struggle with that of the other Irish Diaspora communities; the Jewish and Cypriot communities in Britain and Algerians in France to similar events in Palestine, Cyprus, Algeria and France.