The growth of interest in urban studies in recent years had induced scholars to take a new interest in Irish immigrants to Britain during the nineteenth century. The Irish encountered most of the problems of immigrants and were the subject of much comment from contemporary English writers. Moreover, since they constituted a small but homogeneous minority, easily discernible in the larger community, they can be conveniently studied in depth. The purpose of this article is not, however, to do this so much as to enter a few caveats for anyone thinking of specialising in one facet of Irish immigration to Britain, namely, juvenile deliquency. The subject of delinquency among Irish children in Britain, which has intrigued Englishmen for at least 150 years, has taken on new importance in recent times, partly as a result of the revival of an old allegation that there is a connexion between Catholicism and crime. Formerly, the assertion was made by ultra-protestants, especially Recordite evangelicals. Now it is being made by some English Roman Catholic priests. While this article will not deal conclusively with the overall question of a connexion between Catholicism and crime, it is intended to argue that, at least as far as Irish immigrant catholics in nineteenth-century London were concerned, such a connexion could not reasonably be said to exist. In the course of doing so, it will contend that, even granting that the Irish were a police problem as distinct from a crime control problem, there is, nevertheless, evidence of police prejudice against them. It also aims to show that destitution and vagrancy were common among London’s juvenile poor, especially the Irish, and that destitute juveniles were frequently classified as delinquent juveniles and treated accordingly. Finally it will put forward evidence to suggest that some English protestant philanthropists, including some evangelicals, have through over-generalisation, and perhaps unwittingly, caricatured the London Irish.