National Rail Fares Manual released

Try inputting Thurso to Penzance...

I've seen something about the 5p Virgin fares being in relation to their Traveller scheme, which is a reward for regular first class passengers. One of the benefits is free travel in First Class at weekends, so perhaps the 5p fare is a token to give them a valid ticket.

another thing I spotted was that there are some £999.00 fares, often "child flatrate fares" but one to really catch my eye was that it apparently costs this much for a bike ticket between Edinburgh Waverley and Haymarket stations (1.5 miles apart, and almost certainly quicker to cycle between them than get your bike onto and off a train).
I presume this figure means that the system knows the fare exists but doesn't know what price it truly is.