Originally Posted by caz
That's not quite what I had in mind, Robert.
I wondered if it was belt and braces. Try the effects of exposure first, and if that doesn't do the trick, or is taking too long and becomes unbearable, resort to the strychnine to do the job for you. I mean, one can only [successfully] commit suicide once, and the length and level of suffering involved with each potential method would presumably be an unknown quantity and differ from person to person. Two years ago, one of my brothers (with a long history of depression) drank himself almost into a coma before jumping to his death from his high-rise balcony.
If the man on the moor went there alone and determined to die, he had to make sure his available/chosen method(s) would work and not just leave him dying slowly of hunger and thirst. Alternatively, it might have taken him hours to pluck up the courage to take the strychnine, by which time the cold December night air would already have taken effect. But the fact he wasn't suitably dressed for the trip and went despite the warning about not getting back in daylight looks like part of the plan.
Sorry about your brother Caz (that mongrel Black Dog as Churchill called it) but I think your last paragraph is the most likely, took him time to pluck up the courage and on a cold night hypothermia, which he barely noticed in a depressed and suicidal state, got him.