Pre-heat oven 180 C.
In a large mixing bowl, mix sugar, butter and vanilla extract together.
Add mashed bananas, egg, flour, baking soda, salt and cinnamon and beat with an electric mixer on medium speed for about a minute or until mix is combined.
Stir in walnuts.
Pour mixture into a greased 8 inch loaf tin.
Bake for 1 hour or when a toothpick is inserted and it comes out clean.
Allow bread to cool before serving.