A friend and I were travelling around London on a Saturday a few weeks back, to see the steam on the Met. We'd bought Off-peak travelcards. A member of London Overground barrier staff (I can't remember which station it was now) tried to tell us that they are not valid before 0930, even on a Saturday (the barriers would not let us through)! Since it was almost 0930 at the time he let us through anyway, but we both have a suspicion that he was talking rubbish. Was he?