The answer may lie in what’s known as the “cross-race effect”.

The effect explains that it may be easier for individuals to recognise those within their own race than those who exist outside their race. Experimental Psychologist Dr. Lisa DeBruine explains that with “every face you see, you include in an average in your brain, and then you remember people by comparing them to that average.” In turn, this may explain why those belonging to a certain ethnic group, may think that those belonging to another all look the same. “But if people move to a new place and [they] get more experience with an ethnic group, this will affect [their] internal average and they get better at individuating people.”

In other words, when you are compared to someone you think you look nothing like by someone outside your race, there's a high chance that person doesn't mix with a variety of ethnic groups.

It makes sense, and would explain why my white friends disagree with my so-called doppelgängers while a white woman in Bath – not known for being the most diverse city in the country – would think I look like someone who's sold out arenas across the world.