Charles Ellson wrote:

In fact is there a clear list anywhere of which pairs of stations
definitely
are and aren't valid through interchanges on a single ticket?

For Oyster :-
http://www.whatdotheyknow.com/reques...on_interchange

There are also "emergency OSIs" mentioned in :-
http://www.oyster-rail.org.uk/out-of...terchange-osi/
(PVAL = passenger validator)

Thanks. I assume the regular ones are also valid for paper tickets?

I'm surprised that Aldgate & Aldgate East aren't a regular OSI - the number
of times that a Hammersmith & City train is nowhere to be seen would make
that a sensible route.

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