A web site can set a "cookie" in your computer so that it knows when you revisit - we do that on this forum, in fact, to ensure that you can stay logged in rather that have to log in again every time you visit.

I've long wondered if some airline booking systems offer you a good price as a new visitor, then creap up the price when you come back a few minutes later to maximise the fare charged ... and it sounds like a similar technology might be in use on some of the train ticket sites.  With non-regulated fares, it's a free market as I understand it, so whilst we might not like the practise, it wouldn't be breaking any rules.

I'm all in favour of people getting the lowest fare for their journey; it's up to the operators to provide a sensible pricing scheme that doesn't leave "give-away" holes, and frankly I thing everyone (inlcuding them) would do better with an easier system that Joe-in-the-Street can understand, rather than something that feels like a game and a gamble when you want to book. I do worry slightly about "overbooking" to help skew stats and it's not something that I've encouraged. But with 2 out of 5 evening commuter services from Swindon to Melksham cancelled last week, no doubt there were a lot of train tickets sold for people who didn't  end up using the train to get to Melksham