Colin Rosenstiel wrote:

My Cambridge to Underground Zones 1 & 2 tickets don't get eaten at
East Putney which is much more baffling.

Only because you've forgotten the answer! This was covered in a thread
you initiated here in January 2003, which included these two
explanations:

From Clive Feather, 7 Jan 2003:
"The magnetic code contains a common portion, an LU portion, and a
National Rail porton. To a first approximation, LU gates don't
understand the NR bit of the ticket and vice versa; they'll simply note
that both parts are marked active and play safe, giving you the ticket
back."

From Paul Corfield, 6 Jan 2003:
"Any ticket with any National Rail validity will always be given back.
The gate cannot know if you have used the NR validity or even if it is
"beyond" the exit point of the gate itself - e.g. you used the NR bit
between Cambridge and London but the ticket isn't reset to reflect this.
You then enter the LUL system and record an entry. The gate at East
Putney says "has this ticket got the right validity from where it
entered (LUL) to where I am? Oh yes that's OK. Oh look this has some NR
validity - don't know where but I'd better give the ticket back in case
that's the next bit of the journey". "

http://groups.google.co.uk/group/uk....7659a88aadfe9/

--
Richard J.
(to e-mail me, swap uk and yon in address)