In message .com, Earl
Purple writes

David Walters wrote:
The caught outside his zones bit is the key. A paper ticket user
that gets on in zone 1 with a zone 1 only ticket going to an ungated
zone 4 station might get caught by an inspection. A pre-pay user
will be okay if they get stopped and if they don't could "forget"
to touch out to save themselves some money.

and what about someone with a zone 1 season AND some pre-pay on their
oyster?

They can travel to any ungated station outside (if it has a touch-out,
like a DLR station). If an inspector comes outside of zone they just
say they are going out of zone which is allowed as they have some
pre-pay. Then when they get to the other end they just don't touch out.

The system is unlikely to catch them at the moment, although if Oyster
gets expanded beyond London there is less opportunity for this.

--
Paul G
Typing from Barking