Preheat oven to 180C. Lightly grease a loaf tin or line with baking paper.
Beat Soften Butter and Sugar together in a large bowl until creamy. Add Eggs, one at a time, beating well. Add Rum, Rum-Steeped Sultanas and Walnuts, then fold in Flour and combine well. Spoon the mixture into prepared loaf tin, smoothing top.
Bake for 40-45 minutes or until cooked. Cool in pan for 5 to 10 minutes before turning onto a cooling rack because the cake is fragile.