Cream margarine until soft and add sugar and beat until light and fluffy. Add the eggs one at a time, beting well between each addition. Mix in marmalade, sultanas and flour. Turn into greased and bottom-lined deep 18 cm cake tin. Level the surface, and bake at 180ºC or 1 1.5 hours or until a skewer comes out clean. Cool for 15 minutes and turn out onto rack to cool completely.