R.C. Payne wrote:

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.

The first time I changed at Stratford, I fell foul of the mess of this
station. I was arriving by Jubilee, and departing by central, on prepay.
When I arrived at the gateline off the Jubilee platforms, I asked the man
there whether I also had to touch in on the central line platforms, as I
was already using my oyster here. He told me I didn't have to, so I
didn't, and the obvious problem occured when I arrived at my destination:
it wouldn't let me out of the gates because I was supposed to have touched
in on the central.

Nice! Despite using the station almost every day I have never seen anything
about this.

Do you have to touch in going the other way? And do you get charged for two
journeys?

It's chaos like this (as well as the National Rail problem) that makes me
seriously doubt I'll ever succumb to Oyster Pre Pay.