Bill Bryson once remarked that there is a tradition that has to be observed when catching a train.
At the ticket office, you ask the clerk when the Bradford train is due. 'It's waiting on platform 3'
So you go to platform 3, which has a display showing that the train due to depart in two minutes is for Bradford. There is a train. And there is a station employee. And there is someone asking him 'Is this the Bradford train?'. 'Yes', he replies.
Even though you have just heard this, you ask him 'Is this the Bradford train?'. 'Yes' he replies, again.
You look at the train and point at it. 'This one?' you ask. 'Yes', he confirms.
So you get on the train. But before you sit down, you ask the carriage at large 'Is this the Bradford train?' and someone will say 'Yes'.
Then someone will get up and grab their bag because they want the Ilkley train not the Bradford train. Hopefully, this person has left behind their newspaper and a Kit Kat