Mark hadn't been in Miles' line of sight during that rather pathetic display. He expects that's why Miles had continued on with it - after all, it doesn't exactly suit the image of Very Competent Lord Auditor Big Brother Miles, the image that Miles has been trying hard to project, to fall face-down into the snow. That's also why Mark had stood there, watching and not intervening, because sometimes there's a distinct pleasure in watching Very Competent Lord Auditor Big Brother Miles going thump.

Less pleasurable by far would be watching Lord Auditor Miles dying of hypothermia buried in the snow - there's a miserable chatter of guilt even now, imagining his brother dead and frozen, something he doesn't think he'll ever be rid of - and so Mark, to quiet that unhappy thought, struggles out through the snow to crouch down by his supine - no, prone, that's the one - brother.

"Lay off it," he says with typical brotherly gentleness, warmth, and light. "You're being an idiot."