Mix oatmeal, flour, lemon zest and ginger. Heat treacle, syrup, sugar and margarine or lard until fat has melted. Add treacle mixture to the dry ingredients and mix thoroughly. Mix the soda with the milk and add. Beat well. Turn the mixture into a greased and lined 8 inch square cake tin and bake in a moderate oven, 350°F., Gas Mark 4, for 1–11/4 hours. Turn out and cool on a wire rack. Put into an airtight tin and store for a week before eating.