To take advantage of these prices you will need to prove you are a leisure traveller, on the way to the airport, so you will need to provide either yr flight numbers or yr holiday booking reference. I don't think you will need to give this when you arrive at the station but you may be asked to give them on yr journey from the station to the airport.
Going to the airport on the train is great, you can take a nap, read (even at night), play a game, or just stare out of the window... The other restriction to buying these cheap train tickets from high-wycombe station to the airport is that there must be at least two grown ups travelling together. But another great benefit is that children go free. All children under five go free, and then one child over 5 but under sixteen per grown up travelling by train to the airport.
make sure you leave enough time to get to gatwick airport early enough to eat, shop and so on, so check the times of trains from the station before you go. If you have time to kill at gatwick airport you can always read a book or play a game again! As you have bought yr ticket in advance, you don't need to worry about the opening hours of the station.
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