Orienteer ) gurgled happily, sounding much
like they were saying :

Then there's Dartford. It's hard for customers on the 3 north Kent
parallels to get from one line to the other without going back to
Lewisham which might not be in their zone. Is it permitted to change
trains at either Dartford or Lewisham on a travelcard if you promise
not to leave the station?

An anomaly is that holders of freedom passes can use Dartford station.

and travel to Amersham, Chesham and Watford!

They're in the tube zone system, though.