On 31 May, 18:08, traveller
wrote:
If a passenger says that they didn't hear the card reader emit the
'fail' signal

I can't answer the legal question, but hearing or not hearing the beep
is irrelevant. If you don't see a green light, you shouldn't get on,
because you haven't paid for the journey. In other words, the onus is
on the passenger to ensure they've paid, not on TfL to inform them
they haven't.

(NB I don't necessarily agree with this, I'm just trying to explain
the system)

U