Put 200 g (7 oz) of the dates in a small saucepan with the lemon rind and juice and measurement water. Bring to the boil, then reduce the heat and simmer gently for 5 minutes until the dates are soft and pulpy. Mash the mixture with a fork until fairly smooth. Leave to cool.
Mash the bananas to a purée in a bowl, then add the butter, sugar, eggs, milk, flour and baking powder and beat together until smooth.
Spoon a third of the mixture into a greased and lined 1.25 kg (2½ lb) or 1.5 litre (2½ pint) loaf tin (see
Scatter with the reserved dates and bake in a preheated oven, 160°C (325°F), Gas Mark 3, for about 1 hour 20 minutes or until risen and a skewer inserted into the centre comes out clean. Leave to cool in the tin for 15 minutes, then loosen at the ends and transfer to a wire rack. Peel off the lining paper and leave the cake to cool completely.