"Richard J." wrote:

If you ask for "cheap day return to City Thameslink", surely the natural
assumption is that you want to return from City Thameslink? If you wanted
to return from a different London station, perhaps you should have said
so.

That was my initial reaction, but if we assume use of the ticket machine
rather than the booking office, and further assume (for sake of argument)
that the OP is unfamiliar with rail travel, it's not quite so clear cut, is
it?

The other day I used a machine to investigate options for rail travel from
Brighton to Exeter. The permutations ran to four pages (six buttons per
page, I think), with sundry routing combinations - some compulsory ('via')
and others forbidden ('not London'). That's the kind of ticket choice that
clerks have been known to get wrong, let alone the average punter left to
work it all out for themselves.

Chris