The Post Colonial time period was ushered in by the ending of World War II. During this time, many colonies were gaining their independence. In The Norton Anthology of English literature it stated that “In winning a war, Great Britain lost an empire” (1832). It started in Southeast Asia, colonies in India and Pakistan gained their independence. This only began to spread to Africa and the Caribbean. This decolonization going on worldwide helped to usher in a new time of writing and literature deemed “post-colonial writing” (1832).
After the process of decolonization concluded, there was an almost immediate reverse colonization happening in England. People from the other colonies for various push-and-pull factors began migrating to England. These migrants came from all around the world primarily due to the post-war labor shortage. These migrants were not always welcomed in with the same status as other British citizens, which caused friction amongst them. This friction helped further postcolonial writing because it caused Britain to rethink its national identity. London, which had always dominated culture, politics, etcetera was finally transforming from this consistent, almost elitist, example to include other dialects, and other cultures. This gave confidence to other prior colonies to start embracing their own unique and individual culture. A prominent and well-known group that emerged from that was the Beatles.
From the 1960s onward London was no longer the defining city for culture in the United Kingdom, even though its parliament was still dominant until 1999 the following governments came under much pressure from the outside world. A key figure was installed as prime minister as the first member of the Conservative Party took power, Margaret Thatcher. This was a big shift from the predominantly Labour Party's that were prominent before.
These were the primary historical events surrounding postcolonialism and were largely what helped it to grow.