I'd be interested to hear people's thoughts on this. Recently I had to use the SE High Speed from Chatham to London. As I already hold a priv season ticket from Chatham to London terminals, (not valid on HS1) I buy a priv upgrade at 90p. I arrived at Chatham ticket office 13 minutes prior to the train departing and found a queue caused by someone trying to get a refund. I waited in the queue until the train was arriving, but the queue still had not moved so I left and boarded the train. At this point I haven't boarded the train without a valid ticket as you only need the upgrade beyond Gravesend. I went to find the conductor on the train to buy an upgrade, but she said that she didn't have a working ticket machine, and told me to buy the upgrade on arrival in London. Of course on arrival in London the jobsworth on the barrier refused to sell me an upgrade, instead want to take my details and accused me of fare evasion. I won't say how things turned out, just want people's views.