It starts in March 2017 with a row over a promotion. An internal selection competition opens up for ordinary garda members to join an Armed Support Unit, one of the elite groups, the kind then operating round the clock, high visibility, armed checkpoints in Dublin to tackle the deadly Kinahan/Hutch gangland feud. Or at least it could start there. Maybe it starts back in July 2015 when John Barrett, the executive director of human resources of An Garda Síochána, puts noses out of joint flagging up concerns about irregularities in the finances of the Garda College in Templemore with its…