SI 109 1984 wrote: 4. Where the Board gives notice that a station is unattended or the booking office is closed, or where any person is instructed by an authorised person to board a train at a station without purchasing a ticket at the booking office so as not to delay the departure of the train from the station, any person not in possession of a valid ticket entitling him or her to travel may enter a vehicle at that station for the purpose of travelling but that person must obtain a ticket or other authority from an authorised person on the train as soon as practicable after entering any vehicle or from an authorised person on arrival at the station to which such person is travelling by the train.