In message , at
08:00:43 on Fri, 1 Sep 2017, R. Mark Clayton
remarked:
It's difficult to think there was a very similar reason since the buses
have been OPO/DOO/whathaveyou for years.

Yes but Edinburgh's won't give change - I saw a foreign tourist put off
because he only had a note.

A tourist I met today claimed that the TfL ticket machines at Heathrow
accepted neither the new £1 nor the new £5. The latter surprises me
more. But he has a plausible account of the conversation with the
roaming helper. I think the solution was for the helper to manually give
old £1s as change for the new fiver.
--
Roland Perry