We are planning to spend a few days in Stamford and are wondering if the train info I've found on the internet is the best way for us to get there. The GNER seems to run approx ever 15 minutes to Peterborough ( where we plan to pick up a car), so it sounds like a commuter train. Will we need to book tickets ahead or should we just buy tickets when we get to the station? We will be returning to London on a Saturday and need to connect to Eurostar,so we do have a schedule to meet on that day. Should we play it safe and book online?

Walk up tickets in UK can cost a bundle more than tickets bought on advance purchase - even just the evening before. The UK has about 26 private rail lines, GreatNortheastern being one and each has own fares and policies. so check internet pricing to see if walk fares are much more expensive - if not buy at the station. Otherwise the advance fares often are not refundable or changeable. A recent problem one Fodorite wrote about was having had booked a discounted ticket and finding out that that train had been cancelled. I was recently on a GNE train and before take-off they said over the PA that if you had a discounted ticket it would be honored only on the train it indicated and you would be charged full fare if it wasn't for this train. actually what may be your best bet is to buy a Days Out of London pass, which gives you two days of unlimited travel over an 8-day period - currently $44 in 2nd class and $78 in first class. Though the area of coverage ends just a tad short of Peterborough (Ely is within the bounds), buying a supplemental ticket from where this pass ends would just be a few pounds- you could thus hop on any train with this pass, walking up and probably also have the cheapest possible return fare from London. These passes are not sold in UK - current prices are for off-peak travel (Nov-feb 29). If you have a third or fourth, etc. person on this pass they would only pay 50% of the pass price. this pass is not valid on airport services, however.

If your question refers to the train from Peterborough to Stamford, booking is pointless and probably impossible.

If it refers to the train from Kings Cross to Peterborough, booking isn't necessary except at a few key dates over Christmas/New Year(in the unlikely event of the train being full, you just stand. It's only an hour). This isn't usually a commuter route: Peterborough is often the first stop on intercity trains to Scotland

It's not quite true that advance booking is spectacularly cheaper (though it's always worth checking the operating compsany;'s website for deals). The walk-up Saver return on this journey of £29.90 (or £26 on trains operated by WAGN) is available on most trains after 0930. The Advance purchase fare of £21 is available on far fewer trains both ways.

Buying a restricted ticket is actually a more dangerous option, as it limits what you can do if anything goes wrong, or if you simply find something more enjoyable to do than hang round a railway station. Train travel on Saturdays, BTW, is widely subject to disruption, and personally I'd buy the more flexible option. You can see all the fares available by going to www.nationalrail.co.uk, plugging in the details then selecting "check fares". Click on the fare descriptor for conditions. If you see a strange-looking fare, click on te departure time and you'll probably discover it's a rogue operator.

Whenever I travel on a GNER from Peterborough to Kings Cross I never bother booking advance tickets for outward or return journey.

If you have not booked tickets (or reserved seats), you will not be denied access to a train, you would just have to join the rush to get a seat.

Quite often, trains bound for Peterborough sit at Kings Cross for a while (often more than one at a time) so you can easily get a seat.

Be prepared for traffic chaos when you drive to Stamford, it does get busy on a Saturday and parking can be difficult, depending on where you are heading to in town.

The railway lines in Britain are not run by private companies. Companies like GNER are companies running passenger trains. From London to Peterborough, you can use GNER or WAGN (West Anglia Great Northern) trains; the latter are commuter trains wheras the GNER trains are expresses calling at Peterborough en route to the north of England or Scotland. For a relatively short journey like this, it's easiest to buy tickets at the station. Travelling from Peterborough to London, it would be best to catch a WAGN train which will have plenty of seats as I think they usually start from Peterborough, whereas the GNER train may have started its journey in Scotland so could be delayed and may not have seats available.

Thank you all for your help and good advice, especially the warning about train disruption on Saturdays. We will allow plenty of time to get back to Waterloo!