Grease a 20cm square cake tin, line with greaseproof paper, then grease the paper.
Mix the flour, baking powder and cinnamon together in a bowl. Put the sugar, honey, dates (stoned and chopped) and apple juice in a pan and heat gently until the sugar has dissolved. Remove from the heat and leave to cool slightly, then add the flour with the oil. Beat until smooth. Add the eggs (beaten) and apples (peeled, cored and chopped) and mix thoroughly.
Turn the mixture into the prepared tin, then sprinkle with the walnuts. Bake in a preheated moderate oven (180C/350F/Gas Mark 4) for 1hr to 1hr 15 mins until the cake springs back when lightly pressed in the centre. Turn out onto a wire rack, peel off the paper, turn the cake the right way up and leave to cool.
To freeze: Wrap the cake in a polythene bag, seal and label and freeze for up to 4 months.
To thaw and serve: Unwrap, place on a serving plate and leave to stand at room temperature for 4 hours.