They're not a random stranger claiming to be a noble. That's false.A random stranger getting an audience with the king of England because they claim to be a noble from some unheard of land? That's tells me they always saying yes no matter how illogical. Nobody has been able to come up with a reason why a background feature would not work for some people.
They are a noble. People (the king, his guards, his servants) are inclined to think the best of them. They are welcome in high society (Buckingham Palace). People assume they have the right to be wherever they are (Buckingham Palace). Other people of high birth (the royal family) treat them as a member of the same social sphere. You can secure an audience with a local noble (the King) if you need to.