Alan OBrien wrote:

Do you have to touch in if you are using a travelcard, rather than
PrePay ? I thought it was only PP users who had to touch all over the
place ?

Only PAYG users need to touch in.

The Conditions of Carriage state that "When you use London Underground and
National Rail services, you must touch your Oyster card on the reader at
both the start and the end of your journey. Where the ticket gates at
stations are open you must continue to touch your Oyster card on the
reader."

That goes for all Oyster cards, prepay and season tickets.

Yes but as discussed before not all passengers can touch in at some starts
and ends, due to lack of readers. I'm also left completely unclear as to
whether readers at National Rail stations with barriers (e.g. Ilford) are
sufficient or whether one has to again touch on to a reader when switching
to the tube.

On a daily basis I don't touch in when interchanging at Stratford, not least
because the readers on the platform are badly positioned given the crowds
the station has to cope with, and I've never had a problem when exiting the
system at a barrier.