A child is considered to have links if they are a foreign national child, a child with dual nationality or a British child of foreign parents / national origin. (frg.org.uk)
As British law recognises dual nationality, there are many who have been both British and something else. (politics.stackexchange.com)
Even marriage does not result in dual nationality, unless it is accompanied by extended stays in the spouse's country. (lawyer-monthly.com)