John B wrote:

But yes, I'm fairly sure there are no London-only routes with catering
of any kind.

I must confess I was finding it hard to think of any -
Paddington-Ealing Broadway, perhaps, or Marylebone-South Ruislip, but
I'm by no means certain of either case. Waterloo-Wimbledon?

However, the wider point that someone commuting from, say, Uxbridge
can't have a drink on the way home while someone from Oxford can be
*sold* one holds true, and has interesting class implications.

Tom