Talk about it here.
"John Smith" was an identity created by the mind parasite Mr Waites when he trapped the Eleventh Doctor in the Hellscape. Within the Hellscape, "Smith" was introverse, feeling pressured to conform with what was expected of him but unhappy with his inability to stop the pain he saw around him. He finally snapped and died by falling to his death whilst attempting to fix a slow clock on the outside of one of the Department of Commonality building's upper floors, and the Doctor woke up. (COMIC: John Smith and the Common Men)