After the Norman invasion the United Kingdom began a long steady process of developing and becoming a world leader on a variety of scales. By the time Henry VIII became King in 1509, a large military and burgeoning explorers meant the United Kingdom was set for a rapid expansion.
By 1820, the United Kingdom had control over 26% of the worlds population. The various colonies included Canada, Australia and India, with the USA having just gained independence. The UK dominated this period almost entirely, having beaten Napoleon at Trafalgar. Both the economy and military prospered in this time as private companies traded on behalf of the crown.
However, as the year 1900 approached, the UK public became more concerned with issues of the empire. It was becoming more difficult to maintain both control and enough funds to govern. By 1945, after two world wars, the UK had no money and very little military to maintain its empire and so many countries were granted independence and the commonwealth was formed.