The major difference in the 20th Century Britain had been the growth of a multicultural society
Until 1945, whites made up 99.8% of the British Population, by 1979, this figure went to 96%
The vast majority of non-white immigration took place between the 1950's and 1960's and this was due to the decline of the British Empire (restyled the Commonwealth in 1949)
Colonial residents were legally British Citizens until the 1962 Commonwealth Immigrants Act redefined their status (so very few people from the 'New Commonwealth' came to Britain)
