Wolfgang Schwanke wrote:

The part I don't understand is why they do this in the first place. I
thought the LU system is rather "fraud safe". You can't get in or out
of the system without some form of valid ticket (except by climbing
over the gates or taking a detour to a DLR station), so hunting down
fare dodgers should be pointless. What am I missing?

First there are more than just a few ungated places where you can enter
the system.

Second, there are tickets that will open gates, but the holder is still
not permitted to use them. Others have alluded to some of these, and
you'll find more in the archives of this newsgroup.
--
Michael Hoffman