As Bridlington has both a ticket office and a ticket machine you must purchase a ticket before you board - unless both the ticket office is closed and the machine is out of order. If the ticket office is closed and you wish to pay with cash, or the machine does not sell the ticket required, you must obtain a 'promise to pay' from the ticket machine. If both are in operation and you don't purchase a ticket, you are risking a penalty fare.That is exactly what I have found they will all be fine with me showing my railcard and paying for ticket on train so I’m a bit concerned if I ever do meet one of these revenue officers would they let me pay for ticket as I normally do or would they automatically give me penalty fare?
Arriving with insufficient time to purchase a ticket is not a valid excuse. As the TVMs have been out of order conductors and revenue officers are currently being more lenient on board, but in the near future on board ticket sales will be tightened up when you've passed a working opportunity to pay.