It’s a super report, and a classic example of the ‘Swiss cheese’ model:
* late changes to design and function of coupling / connection systems
* BPIC not designed to correct standard (as a result of above)
* BPIC positioned in a place where it could be operated inadvertently
* Procedure for timing of brake continuity test had the potential for a different interpretation to the intention of the procedure relating to the coupling / connection procedure for this stock
* VCB opened and did not close, preventing use of Rheo brake
* Train manager didn’t have a functioning radio with him for communication with driver
It is likely that if any of these had been different, the incident would not have happened (or the train would have been brought to a stand at Waverley)
Fortunately, a couple of the swiss cheese holes were not aligned:
* the train had a route set through Slateford / Haymarket to Waverley, ie no conflicting movements set against it
* the driver had the presence of mind not to press the GSMR REC button
* the driver was able to contact the signaller, and the signaller was able to action the setting of a route through Waverley in short order
* the train manager was sufficiently aware of a problem, and pressed the passenger alarm button in the train (albeit it took two attempts).
Had one or more of these been ‘aligned’, then the consequences could have been rather worse.
A lucky escape, but a very unlucky chain of events.