Colin Rosenstiel wrote:

Not sold as that AIUI. Cambridge to Zones 1 & 2 Saver Return: 29.00,
with Network card: 19:15 66% of 29.00=19.14

This is true - but it's an odd anachronism, almost, that applies only
to TfL but not any other PTE or similar[1].

[1] Actually, that's not quite true. Railcard discounts are available
on through coach/rail fares involving the Stagecoach X5 and VT99 rail
links and probably others. The discount is on the complete fare, not
the train fare alone!

Neil