National Rail Conditions of Travel (
https://www.nationalrail.co.uk/National Rail Conditions of Travel.pdf). Most prevalent bits for you
6.1 You must hold a valid Ticket or authority to travel before you board a train where there was the opportunity to buy one unless one of the following circumstances applies:
6.1.1 At the station where you start your journey, there is no means of purchasing a Ticket, either because there is no Ticket office open or a self-service Ticket machine is not in working order, or will not accept your only available method of payment (card or cash); and where notices indicate that Penalty Fares may apply from that station, you purchase a Permit to Travel if there is a working Permit to Travel issuing machine at the station where you start your journey – see Condition 10 for more information about Penalty Fares; or
6.1.2 The station is staffed, and you are specifically permitted to board a train service by an authorised member of staff, or you have received a written notice or heard an audible announcement to this effect; or
6.1.3 At the station where you start your journey, there is no means of purchasing a Ticket, because
- 6.1.3.1 the Ticket office is closed; or
- 6.1.3.2 a self-service Ticket machine is not in working order, or will not accept your preferred method of payment (card or cash); or
- 6.1.3.3 You have a disability and Ticket purchasing arrangements at the station you are departing from are not accessible to you.
In these cases, you must, as soon as you are reasonably able, buy an appropriate Ticket to complete your journey. The price of the Ticket you purchase will be the same as if you had bought a Ticket at the station from which you first departed.
INFORMATION: This means that you should buy a Ticket from the conductor on the train if there is one available; at an interchange station provided there is sufficient time before your connecting service; or, if neither of these is possible, at your destination
unfortunately ( and no judgement from me) as explained on your appeal rejection it is your responsibility to ensure you have sufficient time to obtain a ticket or promise to pay prior to boarding the train.
Essentially, if you board a train without holding a valid ticket then you are in breach of the Conditions of Travel and liable to prosecution
unless you have a specifically defined good reason for not having a ticket. Being unable to buy a ticket at the station with cash because there is no open ticket office and no working ticket machine is one of these reasons, but even then you might be required to obtain a (free) "Permit to Travel" ticket from a machine prior to boarding a train.