Heat oil in a pan on the stove. Add Onion and cook until clear. Add Can of Tomatoes and sugar to onion and bring to the boil. Add Gravy Powder and stir through. Add salt and pepper to taste. Take of Stove. Place Lamb Shank in Slow Cooker and poor Sauce over it. Place lid on and cook for 4Hours on High.
NOTE....Left over Sauce is nice on toast for Breakfast.