TKD wrote:
I was reading something on the net about the layout of Stratford station
on the Central Line. I have been there before a few years ago, but I
don't remember the layout myself. The page indicated that it's possible
to transfer between Central Line trains and mainline trains across the
platform. Doesn't this imply that it's possible to board a tube train
without entering a fare-control area? If so, how does one get charged
the proper amount on one's farecard upon exit on the other end of one's
journey?

If arriving at Stratford on a mainline train and using an Oystercard to
continue your journey you need to touch in before boarding the tube (or
v.v.) - there are around 6-8(?) readers on each of the Central line
platforms.

I suppose the same holds if one enters the platform area from the station ticketing hall?

The whole station is a fare control area. The only entrance is owned and
managed by London Underground with a tube style gateline. There is a
second gateline between the Jubilee line and the rest of the station so
anyone starting their journey at Stratford or interchanging from the
Jubilee line will be forced to pass a barrier.

Validators on the island platforms are provided for transfer between
'one' services to/from the east and Central/DLR.

It's not the easiest thing to remember - IME, it's easy to forget to
touch in/out on the DLR if you only use it occasionally. Much better
when gates force you to touch in/out at system boundaries.

And how are you charged if you do forget to touch in?

Depends where you touch out. It could be anywhere between £1 and £5.
The journey will be charged in addition to any other journeys you made
that day which might have been 'capped' at a certain price. Worth your
while to rememeber.

If you are changing from the Central Line to NR, you do have to keep
your wits about you.

If you've already got your NR ticket, you have to touch out on the
platform (or it will assume you've gone to Epping or whatever).

But if you haven't got your NR ticket, you have to not touch out on the
platform, but touch out to get you through to the outside of the
barriers to where the NR tickets are sold (if you can find it).

And then you have to be careful not to absent-mindedly touch back in
with your Oyster, but use the paper ticket you've just bought to get
back in through the barriers instead.