Preheat oven to 160 degrees. Spray and flour a large loaf pan and set aside.
Whisk or seive the dry ingredients - flours to salt - well and set aside.
In another bowl, beat eggs, buttermilk and oil using a whisk till well combined.
Add in the sugar and mashed bananas and whisk till the sugar is completely dissolved.
Tip in the whisked dry ingredients and fold the batter using a spatula till incorporated - do not over beat.
Pour into the prepared pan and bake for an hour or an hour 15 minutes till skewer inserted in the middle of the loaf comes out clean.
Allow to cool in the pan and then flip onto a cooling rack to cool completely before slicing and serving.