And if they were travelling to Cardiff Central, there are 'unpaid tickets' desks in the pedestrian underpass prior to the ticket barriers specifically for the purpose of paying ones fare if previously unable to do so...I have used these on a couple of occasions when the Vale of Glamorgan line trains have been sufficiently busy to prevent the guard selling tickets to all on board.
Hi Chris - I haven't used Cardiff central for many years but out of curiosity are these manned desks or
TVM▸ type machines ? If the latter do they accept cash ?
Yes, manned desks, not sure about cash, however they do accept cash for on train purchases so I would imagine the same policy exists at the 'unpaid tickets' desks. They're usually staffed by 3 or 4 people using the same type of machines the guards use on the train. The desks are at the platform 7 end of the underpass, I suspect catering for Valley Lines trains where it is commonplace to buy on board, assuming the guard or train are not too busy, rather than anything longer distance. I've never alighted at Queen Street, so I don't know if they also exist there.