Are there any tricks to know before booking this trip? I think I remember some time ago someone saying something about getting a special card (?) that enabled a discount. Haven't travelled in the UK for years so am a bit rusty on all the tricks.

Buy on the eastcoast.co.uk website, do it as soon as the cheap tickets become available (which is the booking date on the above website).

No special cards unless you are a youth, family, member of the UK armed forces or a senior citizen - all of which require a payment

Other train booking websites:

www.nationalrail.co.uk
www.thetrainline.com

On some trains you may need a reservation. The website will tell you if it's required for a particularly busy service, but you might also want one to make sure you'vs got a window seat on the right-hand side (facing the direction of travel), as that gets you the best view between Durham and Berwick.

The cheapest way is to book as far ahead as possible and on a particular train at a particular time.
With most companies, fares will vary according to the time of travel. It pays to check the website carefully

Thank you all so much. Hadn't thought about where to sit. That's a great tip!

www.thetrainline.com is an independent retailer who charges a fee, whereas train companies' own websites offer exactly the same prices, but don't charge a fee. So using a train company site is a no-brainer.

In this case, www.eastcoast.co.uk offer an extra 10% discount off their own Advance fares, so using the East Coast website to book an East Coast train is an even bigger no-brainer.

London - Edinburgh starts at just £18 if you pre-book well in advance - booking open 12 weeks ahead.

Yes, you read that right. £18. Centre to centre in 4.5 hours. If you flew, the train fare from central London to heathrow/Standsted/Luton airports is £14 before the cost of the flight!!

<i>Other train booking websites:</i>

You can't book on nationalrail and thetrainline is an agent with additional charges