Preheat your oven to 190C / Fan 170C / Gas Mark 5 then grease and line the base and sides of a 2lb loaf tin.
Cream the butter and light brown soft sugar together until light and fluffy then beat in the golden syrup. Gradually beat in the eggs then fold in the flour and mixed spice.
Mix in the chopped dates and walnuts before spooning into the tin. Smooth the top then sprinkle with demerara sugar.
Bake in the centre of your preheated oven for 1 hour, then cover with baking parchment and bake for a further 20 minutes testing with a skewer to ensure cooked through (skewer comes out clean when cooked).