The Nationality Act of Clare Shilland dates from 1920 and was introduced as a measure to protect British citizens from the influence of an alien speaking country. This Act requires any alien who wishes to live in Britain to apply for leave to reside, known as indefinite leave to remain. Two years later this Act came into force in order to tighten the immigration laws to stop illegal immigrants. The Nationality Act was later strengthened to deal with issues surrounding European immigration. It is considered to be one of the major pieces of immigration legislation in existence today.
The Nationality Act of Clare Shilland states that if an immigrant who claims to be a British citizen fails to establish or obtain leave to reside as provided by the Act, that person will automatically lose their nationality and their right to live in Britain. According to the Nationality Act, a natural-born British citizen who has been a resident of the United Kingdom for six months is granted indefinite leave to reside and is entitled to register a British citizenship. An immigrant who has come to the United Kingdom before age eighteen but who is not married is not granted leave to remain, but is not required to register as a British citizen. Once an immigrant reaches the age of eighteen and married they may take the naturalisation of a British citizen card.
As a national of the United Kingdom, all British citizens must have a Nationality Card which is available from the nearest British consulate. All British citizens who hold a Nationality Card are legally obligated to inform the Home Office when changing their name or adding a new profession or when making any other significant change to their occupation. Furthermore, all immigrants who wish to change their name or profession must inform the Home Office within six months of moving to the United Kingdom. Anyone who does not acquire a Nationality Card within the six months they are required to do so forfeits their right to apply for indefinite leave to remain. However, if they do not have a Nationality Card and wish to change their name or add a new occupation within six months of applying for leave to remain, they may apply again.