Preheat the oven to 180°C/fan 160°C/gas mark 4. Grease a 1-litre loaf tin and line the base with baking parchment.
Mash the bananas in a large bowl, then mix in all the remaining ingredients. Spoon the cake batter into the prepared cake tin and bake for 50 minutes and up to an hour, until a skewer inserted into the centre of the loaf comes out clean.
Remove the loaf from the tin and allow to cool on a wire rack for 15 minutes. Cut into slices to serve.