"Ian Jackson" wrote in message
...
In article
,
Neil Williams wrote:
My understanding in that situation is that, if you left the train
early on one of those tickets, you would be treated as if you had
completed the journey you did with no ticket at all (as by doing so
your ticket was rendered invalid, and thus it ceased to exist as a
valid ticket).

On the other hand if you were met at the barrier by a staff member who
says your ticket is invalid, you might say `oh I was just looking for
the sandwich shop / phone topup / etc and I'm going to get on the next
train'.

Not necessarily the most plausible story but hard to disprove. Is it
permitted to needlessly change trains ? I can think of any number of
reasons why you might want to.

As a general rule, the type of ticket that does not allow travelling short,
also requires travel on only on specific train (I.e the one that you have
just got off).

(there are tickets that allow you to make a connection at a branch onto "any
train", but the availability of such tickets is dependent on the
availability on the main part of the route. As such, this will always cost
more than a ticket for just the main part would have cost)

tim