United Kingdom - Passport & Nationality - British Citizenship by Descent (1981-11)
Section 11 of the British Nationality Act 1981 converted all Citizens of the UK and Colonies to full British Citizens if they also held the Right of Abode under the Immigration Act of 1971.
The Immigration Act of 1971 conferred the Right of Abode to those Citizens of the UK and Colonies, who, amongst other things, had been resident in the United Kingdom for some time (usually five years or more). Some British Citizens are unable to pass their nationality by descent to their children. However, children born in the UK are never affected by these rules.