asdf wrote:
There have been reports recently (can't remember if
here or uk.railway) that certain ticket machines south of the river
will, if you try to buy a ticket to KXTL, issue you with a ticket
printed as being to London Terminals, but at the same price as the
KXTL ticket (i.e. more expensive).


Almost...

This information applies to trains from both Brockley and Honor Oak
Park stations, and I suspect applies to all of the Southern Metro
network. When selecting KXTL on the ticket machine, you are confronted
with several options, the two most important being CDRs to "KXTL" and
"KXTL (Not via Underground)". Both of these cost £1.60 (from Brockley
with YP railcard). However, only the latter will print out a KXTL
ticket, saying Not via Underground. If you choose the former, the
machine will merrily print out a London Terminals ticket. I suspect the
staff in the ticket offices are confronted with the same options.

I imagine the OP had the same problem from East Dulwich.

I've only ever had a problem once, when the ticket I had, which was a
London Terminals one, refused to work the gate at KXTL, and when I went
to be let out, the gate staff told me the ticket was invalid. I
insisted that was what the machine had sold me, and he let me out. This
was the first I knew about the whole problem, and since then I've
generally bought the Not via Underground ticket to be safe (except for
when I want to come home via Charing Cross, in which case the Terminals
ticket is very useful!).

As for the difference in the two tickets, I wonder if the first of the
two (the one that doesn't say Not via Underground) is therefore valid
on the Tube between London Bridge and KX. I've never tried it, being
too wary of having my ticket swallowed by the London Bridge gates.