1984 Section Two, Part VIII Analysis (pp. 167-179)
Winston and Julia are completely unaware they are being set up by O'Brien even though he is constructing an idea of the Brotherhood that appears mostly fashioned from Winston's beliefs. He even quotes Winston directly. By doing this, O'Brien is simply using Winston's beliefs to entrap him. O'Brien obtains oaths from them he will later play back for Winston (while torturing him) to demonstrate to him he is morally not superior to members of the Party.
It is ironic Julia and Winston will not at this point consider parting while in service to the Brotherhood, but later after being broken in the Ministry of Love, they will not want to see each other. Further irony is present in O'Brien's discussion of Winston changing his appearance for the Brotherhood because his appearance will be greatly altered from the effects of torture. Orwell even uses the word "irony" (175) to describe O'Brien's presence.
"The place where there is no darkness" appears again in this section. O'Brien seems to understand the reference, which connects him to the Ministry of Love. He is also connected to the Thought Police by his recitation of the rhyme, which is more proof Winston is under constant surveillance even when he thinks he's not.