Postcolonial theory by Paul Gilroy

Paul Gilroy believes that colonial discourses continue inform contemporary attitudes to race and ethnicity in  the post colonial era. Civilization-ism  constructs racial hierarchies and sets up binary oppositions based on notions of otherness.
An example is the British empire, in 1913 the British empire held way over 412 million people,23% of the worlds population.
Britain post-imperial postcolonial melancholia demonstrates its failure to let go of a long gone imperial past reproduces in the present imperial impulse. A target of impulse may be an immigrant

Here is a video explaining the postcolonial theory in more detail below.