It made me stop and think. Mainly because I'd just walked uphill for a mile and any excuse to stop was welcome, even if it was to think, but I did anyway. What might they want? Were they hostile? They looked indifferent, but that might have been the carefully cultivated nonchalnace adopted by the professional (and competent) thug.
I suddenly realised they were assessing me to see if they recognised me, to see if I was a threat. Their world was probably relatively small, insular and dangerous, with the same few people occupying the same few roles in society. Bosses and underlings, suppliers and users, all familiar with each other and all identifiable. Even the enemies, the predators and the traitors, would probably be recognised by these two, so it was imperative in their view that they be vigilant, and causing some discomfort to innocent visitors a small price to pay.
After a moment, they moved aside to let us pass, with not even a cold nod of acquittal. We avoided eye contact and went on our way.
In a moment of clarity however, I understood they were checking me out to see if I was a grass.