>  By contrast, the UK doesn’t bar dual citizens from Parliament-in fact, it even lets Australians vote, and run for Parliament-and I mean sole Australian citizens, who aren’t UK dual citizens.

In fact we have had a prime minister (Boris Johnson) who had been a dual UK/US citizen although he renounced it when he became foreign secretary[1] and one (Rishi Sunak) who had a US green card but didn't go on to get citizenship[2].

[1] https://money.cnn.com/2017/02/09/news/boris-johnson-us-citiz...

[2] https://www.bbc.co.uk/news/uk-politics-61044847