I know it took close to a 100 years to slowly release all occupied territory. But what changed that they would want to give over every holding.
Every Empire learns/knows that you can only govern by consent. By the beginning of the 20th C the lands that comprised the Empire were becoming aware that self-determinism was more beneficial for their people than servitude and allowing the pillage to continue. The Brits to their credit made a better job ( just ) of disposing of their Empire than other contemporary Colonial Powers.