In my innocence I thought that all the GPIO pins would go low at boot-up. I was wrong I should have listened to the old mantra — RTFM. In fact because of the way Broadcom have set out the chip spec there is little apparent logic to the assignment. Page 102 of this LINK gives the assignments should you ever need it.
For those who wonder why anyone would want to have a pin start low, it was driven by a need to force a switched safe shutdown for those who are careless (my family) and this neat little Adafruit switch that pulls the plug when the KILL pin connection goes high. (set high by another push switch switch triggering non-power shutdown code then code in the rc6.d power-off section). I was patting myself on the back for a neat little arrangement only to be gutted by it failing to start-up at all! After the usual check of every connection in sight I finally RTFM. 😥
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