Well Mr Penguin we really need to know the journey details to be able to
take a view. As others have hinted all sorts of issues may come into
play like max journey time, time taken to interchange etc. The most
recent details I have seen show those Hackneys to be a valid OSI - it is
a valid interchange / charging route on paper NR tickets so therefore
PAYG has to follow the same rule.
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I think the simple truth is that the Oyster system hates me as much as
I hate it, and it's deliberately punishing me with the wrong fares...