On Jul 12, 7:34*pm, James Farrar wrote:

" wrote:

Where, on entry to the system, am I told that I will be subject to a
penalty if I don't exit the system within a period of time?

Your use of the phrase "on entry to the system" seems a deliberate
attempt to avoid the truth: it's in the Conditions of Carriage:

6.7.3. Paying as you go on the Underground

[...]

Your pay as you go journey must be completed by touching out at the end
of your journey within a time limit from when you touched in at the start
of your journey. The time limit varies between 70 minutes for the
shortest journeys Monday to Friday up to 4 hours for some longer journeys
on Sundays. If the time between touching in and touching out at the end
of your journey is more than the time limit you will be charged more than
the Oyster single fare for your journey. If this happens, you will need
to call the Oyster helpline so that they may, depending on the
explanation given for the journey having taken longer than the time
limit, refund any over-payment.

Page 18:
http://www.tfl.gov.uk/assets/downloa...7_May_2009.pdf

Thanks for digging that out James, I really should have made the
effort to take a look a bit earlier. It is, as you say, all in the
CoC. I'm sure people will take issue with the vagueness of how the
time limit is expressed.