If you look like someone the system is looking for, there's nothing you can do to whitelist yourself other than wear something on your face, you will be flagged, every single time until a human looks at it, and if they're stopping people, that means being stopped, every time.
If the system has the wrong face in the database, bad luck.
If someone finds a way of preventing detection, say, make up, or big glasses, the system doesn't work any more, as far as I know, even the best facial recognition that only relies on cameras and not depth cameras significantly lose accuracy with either of those.
There are a lot of people in London, the false positive and negative rates aren't usually published and anything above zero means those technical problems happen an undisclosed amount too much.
Did you ever hear the story of the guy with a very common name ending up on the no fly list? The no fly list was for a long time, and I think still now, literally only a list of names, meaning if someone with a common name goes on the list, everyone with that name gets stopped at the airport as the database gets checked to see if they're the same person. Now think what happens if someone with a generic looking face ends up in the police database.