By the mid-1930s Britain had overtaken the United States as the primary destination for Irish migrants. By the end of the Second World War, when Ireland experienced the largest wave of emigration since the Great Famine of the 1840s, this had become overwhelmingly the case. Whereas in the nineteenth and early twentieth centuries Scotland and the north of England had been the favoured destinations for Irish migrants, London and the south-east of England now emerged in this position. According to Jackson, the Irish-born population of London rose by more than half between 1951 and 1961 to reach 172,493. After the Second World War, London became much more socially and culturally diverse. The 1948 Nationality Act conferred UK citizenship on all members of Britain's colonies and in the period up to 1962 (when immigration regulations were tightened by the Commonwealth Immigrants Act) migrants from the Caribbean, the Indian subcontinent and Africa joined European migrants such as Poles and Greek Cypriots to create a increasingly multicultural metropolis.

In Ireland in the late 1950s, major reforms heralded the end of de Valera's policy of economic isolationism. Their effects in terms of job creation, however, took time to come to fruition and unemployment levels remained high. This coincided with the economic reconstruction of London after the Second World War. Recruitment campaigns by employers such as the National Health Service and London Transport were designed to address severe labour shortages. Some of these campaigns were directed specifically at Ireland, where the standard of living was generally lower than in Britain. Improved transport links with the ferry ports of Holyhead and Fishguard also made London more accessible for Irish migrants than before the war. As well as providing young Irish people with better employment prospects, London also offered them the opportunity to widen their social circle.

While remnants of the older London Irish slum enclaves still survived, such as the one studied by the educational psychologist B.M. Spinley in the late 1940s and early 1950s, the capital city became an increasingly attractive option for the Irish. Finbarr Whooley summed up the situation in the immediate post-war years in the following way: ‘London represented an economic bolt-hole from poverty in Ireland.