Preheat oven 180 deg C (360 deg F). Line and grease an 11cm x 22cm bread tin.
In a small saucepan place dates and rum. Bring to a slow simmer and continue to cook until most of the dates have absorbed most of the rum. It will resemble a boozy date jam. Set aside to cool.
In a large bowl place butter and microwave until melted. Remove from microwave and add sugar beat until blended. Beat in eggs one at a time and then add mashed bananas and date mixture. Sift in flour baking powder, bicarb and salt. Mix until combined.
Pour mix into your bread tin and bake for around 60 minutes until cooked through. Cool on a wire rack. Serve thickly cut slathered with butter.