The only real Londoner remaining is old, bitter, kept around for entertainment, defined by tropes from 30+ years ago. They play gangsters in films, or they work in a pie and mash shop, or they go on Business Insider's YouTube channel to tell you about their crimes. And they somehow still find the time to spend all day hanging about cafes and pubs for you to bump into, to remind you of Real London.
so the method has to be autonomous
I imagine that some lab-grown 29-year-old from Woking with a mind honed to identify individuals who fit the profile of Real Londoner (as conceived of by 50 opinion-polled racist builders and their wives in the Midlands) picks a stubborn local who can still somehow afford to live here and passes him along to some creative studio.
stalgivc is the greatest poster of all time