In message , Andrew P Smith
writes

Well, that's as may be in France, but this is the UK. No requirement to
carry ID, and the law doesn't permit the RPI's to demand anything. If
they are not happy with the info you give then they could call the BTP
but that would hold up the train. If they tried to forcibly remove you
from the train that would be assault.

In fact, our RCIs do have the power of arrest; I've heard them
cautioning fare evaders.
--
Kat I've always wanted to be somebody. Next time I'll be more specific.