Hi 142094
I have previously done the assessment in 2007 and was a signaller for a year at Wembley Mainline SCC.
The Assessments I did were fault finding test, listening, reaction test on the pc, maths/thinking based one on mileage, structured interview (although a lot shorter than the train driver's one, as I've now done both). You'll also be tested for colour blindness and it took a whole Saturday in Birmingham when I did it.
Your friend will get a booklet beforehand to pratice on.
Good job a Signaller, really liked it during my time there. Only left due to a very long commute and having a new born at the time. Both my children a lot older now, hence my decision to get back on the railway. But this time as a driver.
Best
Mix107