According to guidance updated on 28 June 2022, individuals can obtain British Citizenship under section 4L of the British Nationality Act 1981 if the Home Secretary considers that the individual "would have been or would have been able to become a British citizen, but for one or more of three specific reasons which are set out in statute". These reasons include: 

• "historical legislative unfairness"
• "an act or omission of a public authority"
• "exceptional circumstances relating to [the individual]"

Historical legislative unfairness would cover scenarios where the law did not treat men and women equally, or did not treat children of unmarried parents in the same way as children of married parents - but there is no limit to the number of circumstances which could be relevant here. Act or omission of a public authority includes errors by government departments or local authorities, but individuals must set out details of this act/omission and how they would otherwise have been able to become a British citizen. Exceptional circumstances cases will be considered on their own merits. In addition, as part of the individual's application, the Home Secretary may also take into account whether they are of "good character". 

Following a successful application under this route, the individual will become a British Citizen otherwise than by descent and can pass on their British citizenship to any children born outside British territory.