Colin Rosenstiel wrote:

Strangely, it was confirmed to me by the Tribute system at Cambridge
that my London Terminals to Brighton Saver Return ticket was valid to
King's Cross Thameslink on my return journey (I went out from Clapham
Junction). This was despite the FCC-only London Terminals to Brighton
Saver Return fare being higher. As I didn't use a barrier at KXTL on my
actual journey (too much luggage) I never tested this claim to
destruction.

Yes...But then Tribute will quite happily issue a Saver Return from
Edmonton Green to Stansted Airport for travel at 08:30 in the morning,
or at least it did last time I made the journey in question.

Bottom line, at present, is that if the journey passes through
Farringdon, you need a ticket either explicitly from/to the appropriate
station or to/from Zone U1.

Cheers,

Barry