Preheat oven to 160ºC/350ºF/ Gas 4.
Sift the flour, salt, spice and raising agent into a bowl. Mix in the oats and sugar. Warm the treacle and margarine together. Make a well in the centre of the dry ingredients. Mix in the warmed ingredients and beaten eggs and beat for 2 minutes. Stir in the milk, fruit and nuts and place mixture in a lined 18cm (7″) square cake tin or a 1kg (2lb) loaf tin.
Bake for 1¼ to 1½ hours, covering after 1 hour to avoid over-browning.
Cut into slices and serve buttered.