Preheat oven to 180°. Grease a loaf tin with butter (or use a silicon non-stick one).
Cream butter and sugar together until light and fluffy in a large bowl.
Add egg and continue beating until well combined.
Stir in diced apples.
Sift flour, cinnamon, nutmeg and baking soda into bowl. Add chopped walnuts and mix thoroughly.
Transfer mixture to prepared pan.