British Subject is a term which has been created out of colonial rule and oppression. It is a term opposite to the term, Citizenship which exists in a democracy, and was used to identify people ruled by the British crown. It is a concept which dates back to Medieval Europe even before the term ‘British Subject’ came into existence. People who lived within the boundaries of the British empire had to owe allegiance to the feudal lords who, in turn were under a mutual obligation with the British crown. So, basically it was an outcome of British colonial rule were the ones living within British colonies had to owe allegiance to the monarch.
When we say British, we are focusing on England, because that was where the British Empire was situated and though, Scotland and Wales were part of Great Britain, they became English colonies after the King of Scotland was overthrown and taken over by the British crown. As time passed, there were certain legal changes made by the legislative body. Scottish people became subjects after the Acts of Union in 1707 and in 1708, the Act of Parliament allowed foreigners to become British subjects.
Now, we have two kinds of subjecthood—one which automatically entitles you with that status by being born in the British colony, and in this case you had to serve the crown for your entire life. In the second case, you are a foreigner who acquires subjecthood which allows you to voluntarily continue with or leave it when you like. As centuries passed, the British Empire spread far enough to rule more than half of the world. There were semi-dominated Empires known Dominions which were given subjecthood after the British Nationality and Status of Aliens Act 1914.
Later after the World War II, a significant change in the meaning of subjecthood took place. British dominions became distinct national identities with their own Parliaments. This includes Canada, South Africa, New Zealand, Australia and many more. They were still British subjects but defied the basic definition of Subjecthood since they were no longer under the obligation of the British crown.
With the British Nationality Act of 1948, three kinds of subjecthood were made. Those who lived within the UK and British colonies came to be known as Citizens of United Kingdom and Colonies (CUKC). The people of Commonwealth countries came to be known as Commonwealth Citizens and those from the Republic of Ireland which is not part of UK became British Subjects without citizenship. After India’s independence in 1947, many Indians and Pakistanis came under the same category as the Irish.
Eventually, by the 1980s, a whole lot of British colonies became independent and the number of CUKCs decreased. As a result, another Nationality Act was passed in 1981 after which people living in the remaining British colonies were named British Overseas Territories Citizens and the ones living in countries and Islands within the United Kingdom became British Citizens.