He discusses initial tests, such as:
For those of us who like trains, it's a nice peek. My maternal grandfather was a yard foreman for the B&O, who let me run a little coal-fired jitney around the tracks, from his lap. I got my first striped railroad cap at four.
These tests include things such as looking at lines of dots on a page, and only checking those that have, say, patterns of four dots. You would have a whole A4 page, and the dots are small, and you only get a short time, so you are unlikely to reach the bottom of he page. The point is to work as quickly and accurately as possible.
In another test you are played, via headphones, a short story, and you then have to answer questions about it from memory.
Then there are the reaction tests. For example, a green light you push a white button, a red light you push a black button, a high buzz you use your left foot, a low buzz your right foot. The sounds start off slowly, and get faster and faster.
If you pass these tests, and the interviews, and medical, and you get the job, there are several months training to do, plus route learning, before you get to drive a train on your own.
With Mike's comments and those of others who have been through the process, you can get a good sense of what it takes in the U.K. and Ireland.