The reach of the British Empire during its extent was remarkable. By the early 1900s, the country had an imperial population of some 412 million people, nearly a quarter of the world's population.
Britain has a long and bloody history of rule and subjugation throughout the world, as would be expected from any empire even a tenth of its size. It lost its grip on many nations after enduring World War II, which left Britain bankrupt and unable to keep control over places like Malay, Palestine and Ghana.
Eddie Izzard has a bit from "Dress to Kill" that sums it up:
"So after the second world war, the whole world was going, 'Come on, Europe, give these countries back. Come on, we had a bloody war, let's give 'em back. Britain?'
'What's that behind your back?'
'Oh, it's India and a number of other countries.'
'Give them back.'
In 1997, Hong Kong was returned to China, completely ending what was left of the British Empire.