Combine water, salt, soy sauce and sugar, stirring until salt is dissolved. Immerse venison leg in liquid and refrigerate 24 to 48 hours. Depending on the size of the leg this mixture may need to be doubled.
Combine all remaining ingredients except olive oil. Remove venison from liquid; pat dry. Rub roast with olive oil then with spice mixture applying as much as possible to make a thick coating.
Prepare smoker with hickory or other hard wood. Smoke slowly for 2 - 4 hours depending on size of roast. Cook until medium rare. Remove from smoker and slice thin. Serve with mustard, horseradish sauce or chutney.
Serves 10 - 12