Who is Johnny "Mother Superior" Swan from Trainspotting and what is their importance?

Johnny Swan is the core group's primary supplier of heroin in the novel. His flat is a favorite haunt of the group, and he himself has been a serious user for a long time. Hence the name Mother Superior. Swan dreams of one day having enough money to move to Thailand, but he eventually loses a leg when he starts shooting heroin into his femoral artery. At the end of the novel, Swan is pretending to be a Falklands War vet, panhandling to fund his addiction.