Preheat oven to 180c (160c fan forced). Grease an 11 x 21cm loaf pan with cooking oil spray. Line base and long sides with baking paper, allowing it to overhang.
Combine flour, soda, cinnamon, sugar and walnuts in a large bowl. Stir in milk, eggs, oil and bananas until just combined.
Spoon into prepared pan. Smooth surface. Bake for about 50 minutes or until skewer inserted into the centre comes out clean. Stand in pan for 5 minutes. Turn out onto a wire rack to cool.