Preheat the oven to 180°C, fan 160°C, gas 4. Grease a 1-litre loaf tin and line the base with baking parchment.
Mash the bananas in a large bowl and then mix in all the remaining ingredients, apart from the toffee sauce. Spoon the cake batter into the prepared cake tin and bake for about 1 hour 30-1 hour 45 minutes, 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. Drizzle the toffee sauce over the cooled banana bread. Cut into slices to serve.