Preheat the oven to 180°C (160°C fan) / 350°F / Gas 4. Line a loaf tin with parchment paper.
Soften the dates: Place chopped dates in a bowl, cover with boiling water, and leave to soak for 10 minutes. Drain any excess liquid.
Cream butter and sugar: In a mixing bowl, beat butter and sugar until fluffy.
Add eggs and dry ingredients: Beat in the eggs one at a time, then fold in flour, baking powder, and cinnamon.
Stir in dates and walnuts: Gently fold in the softened dates and walnuts (and banana, if using).
Bake: Spoon mixture into the prepared loaf tin and bake for 45–50 minutes, or until golden and a skewer comes out clean.
Cool & serve: Allow to cool in the tin for 10 minutes before transferring to a wire rack. Slice and serve with butter or on its own.