Peter had followed him afar off (Ho Petros apo makrothen ēkolouthēsen autōi). Here Mark uses the constative aorist (ēkolouthēsen) where Mat 26:58, and Luk 22:54 have the picturesque imperfect (ēkolouthei), was following. Possibly Mark did not care to dwell on the picture of Peter furtively following at a distance, not bold enough to take an open stand with Christ as the Beloved Disciple did, and yet unable to remain away with the other disciples.
Was sitting with (ēn sunkathēmenos). Periphrastic imperfect middle, picturing Peter making himself at home with the officers (hupēretōn), under rowers, literally, then servants of any kind. Joh 18:25 describes Peter as standing (hestōs). Probably he did now one, now the other, in his restless weary mood.
Warming himself in the light (thermainomenos prōs to phōs). Direct middle. Fire has light as well as heat and it shone in Peter’s face. He was not hidden as much as he supposed he was.