It probably helps that this person has a habit of finding dark and shadowy areas and occupying them in any case. And one person's change of perspective is another's comfort zone, because even several years to get used to Milliways doesn't kill old habits.

Like reading in the comparitive dark, which what Havelock is doing at the moment; sitting comfortably against one rafter, legs extended along another, and altogether blending in quite nicely.