It has to be displayed, this face, on a more or less horizontal plane. Imagine a man wearing a mask, and imagine that the elastic which holds the mask on has just broken, so that the man (rather than let the mask slip off) has to tilt his head back and balance the mask on his real face. This is the kind of tyranny which Lawson's face exerts over the rest of his body as he cruises along the corridors. He doesn't look down his nose at you, he looks along his nose.
Those who actually set out to see the fall of a city or those who choose to go to a front line, are obviously asking themselves to what extent they are cowards. But the tests they set themselves -- there is a dead body, can you bear to look at it? -- are nothing in comparison with the tests that are sprung on them. It is not the obvious tests that matter (do you go to pieces in a mortar attack?) but the unexpected ones (here is a man on the run, seeking your help -- can you face him honestly?).