Back in the days when my government recognised Taiwan, I got a good few Taiwanese diplomats in an English conversation class I used to run. These men were models of their profession to the point of caricature ... and back home in Taipei their English teachers had chosen English names for them, suitable for top civil servants! James, not Jim; Andrew; Stewart; Charles ... not all of them very easy for Chinese speakers, but they used them diligently at all times.
I couldn't help wondering what would happen if they were posted to, say, Iceland or India. Presumably they would still use English as a lingua franca and keep their strange Whitehall identities intact.