To take advantage of these prices you will need to prove you are a leisure traveller, en route to the airport, so you will need to provide either yr flight details or your 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 provide them on your journey from the station to gatwick airport.
Going to the airport by train is great, you can take a nap, read a book (even at night), play travel scrabble, or just gaze out of the window... The other restriction to buying these inexpensive train tickets from the station to the airport is that there must be at least two adults travelling together. But another great advantage is that children go free. All children under five go free, and then one kidover five but under sixteen per grown up travelling by train to the airport.
make sure you leave plenty of time to get to gatwick airport early enough to eat, shop and so on, so check the times of trains from weymouth station before you go. If you end up with time to kill at the airport you can always read a book or play a game again! As you have bought your train ticket in advance, you don't need to fret about the opening hours of the station.
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