To take advantage of these prices you will need to prove you are not a business traveller, on the way to heathrow airport, so you will need to give either yr flight details or your holiday booking reference. I don't think you will need to provide this when you arrive at farnborough-north station but you may be asked to provide them on yr journey from the station to heathrow 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 stare out of the window... The other restriction 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 sixteen per adult travelling by train to the airport.
be sure to leave plenty of time to get to the airport early enough to eat, shop etc, so check the times of trains from farnborough-north station before you go. If you have spare time at heathrow airport you can always read or play travel scrabble again! As you have bought your train ticket in advance, you don't need to worry about the opening times of farnborough-north station.
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