Some do it to explore their ancestral heritage or an unknown part of their identity. Others are hoping to find parents, siblings and new relatives.

More than 40 million people worldwide are thought to have tested their DNA ancestry via companies such as Ancestry, 23andMe and MyHeritage since the first genetic genealogy test was offered to the public in 2000.

Now, people are using their test results in a new way – to apply for citizenship in other countries, DNA experts say.

Prof Turi King, director of the Milner Centre for Evolution at Bath University, said: “The more people take tests and the more people find out their ancestry and who their biological parents are, the more they can use that evidence to get citizenship of a particular country.”

King, who also presents the BBC show DNA Family Secrets, thinks ancestry DNA testing will become an easy and more widespread way for some Britons to gain dual citizenship in the future. “This will only grow,” she said.