To take advantage of the best prices you will need to prove you are not a business traveller, en route to luton airport, so you will need to provide either your 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 give them on yr journey from the station to the airport.
Going to luton airport by train is great, you can sleep, read (even at night), play travel scrabble, or just gaze out of the window... The other caveat to buying these cheap 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 child over five but under 16 per grown up travelling by train to the airport.
make sure you leave enough time to get to luton airport early enough to eat, shop etc, so check the times of trains from the station before you go. If you end up with spare time at luton 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 worry about the opening times of romford station.
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