What do you call it when a a fictional TV show set in non-English speaking country uses modern British accents as the de

This common trope is often called the "Accent Convention" or sometimes "The British-Sounding Foreigner" trope.

In media studies, it is more formally referred to as "Translation Convention." This is the unspoken agreement between the creators and the audience that the characters are technically speaking their native language, but the dialogue has been translated into English for the viewer.

Using British accents specifically for non-English settings—even when the production is American—often serves a few narrative purposes:

• Standardization: It provides a "neutral" or "classically trained" sound that creates a sense of detachment from the viewer’s own regional dialect, helping the setting feel more "foreign" or historical.
• Perceived Sophistication: In Hollywood, there is a long-standing (though often unconscious) bias where British accents are associated with history, authority, or aristocracy. This is why you will frequently hear British accents in films about Ancient Rome, fantasy kingdoms, or medieval Europe.
• The "Exotic" Effect: It effectively "others" the characters from the modern American viewer, helping to establish that the world they inhabit is distinct from the viewer's reality.

You might also hear it referred to as "The Received Pronunciation (RP) Standard," as this specific type of British accent is the one most commonly defaulted to for these roles.