[shellac]

Then somebody needs to let the government know, because the relevant 1981 act is "[a]n Act to make fresh provision about citizenship and nationality". In that 'British subjects' are a quite limited subset of citizens. Most British people are citizens, not subjects.

https://www.legislation.gov.uk/ukpga/1981/61/contents

[lovich]

What’s the difference? I’m not knowledgeable enough about English law to parse this

[shellac]

My (really limited) understanding is that 'British subject' was the status of people in the British empire. It's now reduced to just some people born pre-1949 in Ireland and India. They have many of the rights of citizens, and can become citizens via a simpler route than other non-nationals.