Preheat the oven to 160C/Gas 3/fan oven 140C. Line the base and long sides of a 900g/2lb loaf tin with greaseproof paper, buttering the tin and paper.
Tip the flour, cinnamon, butter, sugar, 2 tablespoons of the honey and the eggs into a large mixing bowl. Mash the bananas and chop the dates (kitchen scissors are easiest for this) and add to the bowl. Beat the mixture for 2-3 minutes, using a wooden spoon or hand-held mixer, until well blended.
Spoon into the prepared tin and level the top. Scatter the walnut pieces over. Bake for 1 hour, then lightly press the top – it will feel firm if cooked. If not, bake for a further 10 minutes.
Cool for 15 minutes, then lift out of the tin using the paper. When cold, drizzle the remaining honey over. Cut into thick slices.