They tried to solve the problem from the wrong angle, and it turns out that the high cost of taxis, while suboptimal for sure, might not be entirely for no reason.
[1] https://tfl.gov.uk/info-for/taxis-and-private-hire/licensing...
For a private hire vehicle (the kind you telephone or use an app to book), the price is under £700 (under £500 if the driver speaks English).
That doesn't seem unreasonable. The GP comment was referring to the American system where the license are traded at very high costs (tens, hundreds of thousands of dollars).
https://tfl.gov.uk/info-for/taxis-and-private-hire/licensing...
The private hire license avoids the need for "the knowledge" and to have the traditional London black cab. There are still fees involved, of course - but becoming an Uber driver is much less demanding than becoming a black cab driver.