It's easy enough to keep track of, the only bright pinprick in the vast expanse of desert - and in any case Crowley has not gone far. Only high, beating back and forth for altitude, wings tearing low, thudding sounds out of the wind.

That they can fly at all is a wink and a nudge to physics - and yet. And yet it's thrillingly, viscerally physical, as satisfying as the pounding earth under a runner's feet, still bound by breathless thin-air laws that put only muscle and sinew and a lot of empty space between them and a long drop with a sudden stop.