1.Preheat oven to moderate, 180C (160C fan-forced). Lightly grease and line a 20 x 30cm slice pan.
2.Combine dates, water and caster sugar in a saucepan over medium heat. Cook, stirring, 10-15 minutes, until dates have absorbed most of the liquid. Set aside to cool.
3.Meanwhile, in a bowl, using an electric mixer, cream butter, brown sugar and syrup together, until light and fluffy. Sift flour and soda over butter mixture. Fold in lightly. Add oats; mix well.
4.Press half the oat mixture into base of prepared pan. Spread date mixture over the top.
5.Mix walnuts through remaining oat mixture. Crumble over date mixture, pressing lightly. Bake 30-35 minutes, until golden. Cut into slices when cold.