The Immigration Act 1971 was a major piece of UK legislation that reshaped immigration control and defined who had the right of residence in the country. Introduced by the Conservative government under Edward Heath, it came into force at a time when Britain was adjusting to the long-term effects of post-war migration from Commonwealth countries.

At its core, the Act created the legal concept of “patriality,” meaning that only people with a strong ancestral connection to the United Kingdom—such as those born in the UK or with a UK-born parent or grandparent—had an automatic right to live and work there. Others, including many Commonwealth citizens who had previously enjoyed relatively free movement to Britain, became subject to stricter immigration controls.

The legislation also consolidated earlier immigration rules into a single system of entry and stay permits, giving the government greater authority to regulate who could enter and remain in the country. It marked a clear shift away from the more open Commonwealth-era migration policies of the 1940s and 1950s.

The Immigration Act 1971 is often seen as a turning point in modern British immigration history, laying the groundwork for the system that continues, in modified form, today. While it aimed to create clarity and control, it also had long-lasting social and political impacts, particularly on Commonwealth communities who had already settled in the UK.