To be honest, the torch inside the room seems out of place. Based on the logic you spoke about, who would put an ad-hoc version of a flaming mace in a prisoners cell?
To be honest, why would they bother leaving Any light for the prisoners? They're there to stay there, not have light to style their hair by. Let them sit in the dark!
Torches throw off a ton of smoke, are very hot, and generally are over bright and will blind you more than they will help you see. (This is why you hold a torch BEHIND and ABOVE you, not thrusting it toward whatever you're trying to see... Because then you'll be staring at a big ball of fire while whatever you're trying to see jumps out and attacks you)