To take benefit of these prices you will need to prove you are not a business traveller, en route to luton airport, so you will need to give either your flight details or yr holiday booking reference. I don't think you will need to provide this when you arrive at peterborough station but you may be asked to provide them on yr travels from peterborough station to luton airport.
Going to luton airport on the train is great, you can sleep, read a book (even at night), play travel scrabble, or just gaze out of the window... The other restriction to buying these cheap train tickets from peterborough station to luton airport is that there must be at least two grown ups travelling together. But another great advantage is that children go free. All kids under five go free, and then one child over five but under 16 per adult travelling on the train to luton 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 peterborough station before you go. If you have time to kill at luton airport you can always read a book or play travel scrabble again! As you have bought yr train ticket in advance, you don't need to worry about the opening hours of peterborough station.
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