I had a similar incident to Ms Pickett's, but - to their credit - the gate staff adopted a different stance. I had been commuting from St Albans to St Pancras for over 30 years. But one Wednesday my KeyCard didn't let me out through the STP barriers. With horror, I realised it had expired the day before. Unusually I hadn't extended the monthly renewal to the fifth week's Friday, expecting (at renewal) to take few midweek days off. Being a plastic card, there was of course no date on it. And the barriers at SAC had (again unusually) all been open; so I got no expiry alert before starting the journey. I politely explained the situation to the STP gate staff, asking them to let me through so I could buy a day return at the nearby ticket office. Rather to my surprise, I was allowed to do this, and I even returned to the gate moments later to show the staff the (albeit late) outbound ticket; I didn't want her to think I'd conned her! All praise was due for this common sense, especially towards a customer who'd contributed over £120,000 to the TOCs' coffers.