In message , Peter Smyth
writes

"Paul Terry" wrote in message
...

And why make a mixed-mode entry charge when in many cases the journey
is likely to be entirely on NR?

I think the reasoning is that all travelcard seasons cover at least 2
zones. Therefore the maximum you can pay as an extension is 4 zones
including Z1, which is £4.20/£3.40 (ignoring trips to Amersham etc).

Ah, that would make sense. Thanks.
--
Paul Terry