Soak the bread in a little water for an hour, then squeeze the moisture out. Combine the flour, baking powder, mixed spice, sugar, butter, fruit, beaten egg and milk. Mix well.
Line the bottom of a 22cm (9in) square tin with half of the pastry and spread the mixture over, then cover with the remaining pastry. Make a few diagonal gashes across the top and bake at 190°C/375°F/gas mark 5 for about an hour. Sprinkle the top with sugar and allow to cool in the tin, then cut into 24 small squares. (A square of this size used to be sold for a halfpenny.)