In message .com, Paul
Oter writes
Journeys entirely within the travelcard area are not affected, it
says...

Indeed, as there have never been time limits on use of travelcards (once
they start to be valid after the morning peak).

But this brings in some other silly anomalies, e.g. on a slow train you
could use a 1-day travelcard bought, say, from Luton quite validly on
the crowded section from King's Cross to Elstree, but not on the section
from Elstree to Luton, where the passenger loadings will be
significantly lower.

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