shorting the track circuit would have shown up in the signal box, and while the track in rear of the “frigged” signals was track circuited, I’m not sure if the portion of like ahead was, as my understanding was that that went into an IB section..
and while the “driver” had only driven diesel shunters, Tbf at the time, 1963, only a smallish proportion of BR drivers on the LMR had, and where are you going to get a recently retired driver with mainline loco experience from?