Earlier quoted context omitted.
I really fail to see the difference between this and Russia's fine.
If your flight is redirected due to weather/etc. to some British commonwealth country, then you might be grabbed upon landing. Or if you are a really big fish, your plane might be forced to land on a crown-controlled land.
Even more unlikely is the crown exercising the kind of power you're talking about. Never mind that Charles isn't the King of the majority of Commonwealth countries.