Why did Black and Asian immigrants from the Empire not come to Britain in substantial numbers until after WW2?

Question

The Windrush saga in the British media has thrown light on the situation of post-WW2 migrants from the British Empire - particularly the Caribbean, India and Pakistan - who came to the UK in the immediate aftermath of WW2 under the Attlee government and so began modern British immigration.

My question is - why did these migrants come in at that time in particular, and why had they not come previously? Most of the now-ageing immigrants describe having thought of themselves as British subjects, and therefore eligible to move throughout the Empire. And indeed, some migrants did move to the UK during the earlier part of the Imperial era. As early as 1892, an Indian migrant was elected to the House of Commons, and there were a number of notable individual Black/Asian people living in the UK in the 19th Century, as well as small communities in certain specific places. I cannot find any references to restrictions on Empire/Commonwealth migrants prior to the Commonwealth Immigration Act of 1962.

My question is - why did substantial numbers of Empire immigrants not move to the UK during the earlier periods of Imperial history, and why did so many come in at that particular point in time? I am vaguely aware that it was partly because the socialist Attlee government actively encouraged them to come, but I would have thought that, given the substantial disparity in GDP per capita between Britain and some of the other nations of the Empire, there would have been significant pull factors in place previously anyway. Also, what were the motivations (ideological and practical) for the Attlee government in encouraging their arrival?

Answer 1

Because the British Nationality Act gave Commonwealth citizens free entry into the United Kingdom in 1948. This coincided with post-war labour shortages. As a result, market demand recruited large numbers of migrant workers into Britain. It is this availability of jobs, not mere disparity in GDP, that attracts immigrants.

However, it's inaccurate to characterise the immigration as taking place at any particular "point" in time. British Indian and Black populations didn't suddenly explode right after 1948; the flow slowly increased over many years. As late as five years after the war had ended:

The non-white population began to grow but even in 1950 the total numbers in the whole of Britain were probably less than 50,000.

_{Thompson, Francis Michael Longstreth, ed. The Cambridge social history of Britain, 1750-1950. Cambridge University Press, 1992.}

In fact, the biggest proportional increase in the British Indian population didn't happen until the 1960s when it more than quadrupled in a decade. A notable factor is the exodus of British Indians from Africa, who had migrated there during the days of the Empire. Faced with intimidation, discrimination, and in the case of Uganda, outright forced expulsion, many of them utilised their British passports and resettled in Britain.