Preheat the oven to 180C/350F/gas mark 4
Use a 900g/2 lb loaf tin.
Grease and line the loaf tin. Cream the butter and sugar in a small bowl until light and fluffy. Add the sour cream and mix well. Gradually beat in the golden syrup. Transfer the mixture to a large bowl. Stir in the sifted dry ingredients and potato. Pour into the prepared tin and bake for about l 1/4 hours. Stand for ten minutes before turning on to wire rack to cool. Spread the cold cake with icing.
Lemon Icing: Sift the icing sugar into a small heat proof bowl. Stir in the butter and enough lemon juice to make a stiff paste. Stir over hot water until the icing is spreadable.
