Put the walnut pieces, garlic, olive oil and lemon juice in a blender and work till smooth. Add the yoghurt (this can be low-fat yoghurt if you wish) and blend in quickly. Season with salt and freshly ground pepper to taste.
Transfer to a serving bowl. Peel and finely chop the cucumber and stir into the dip. Serve chilled with crisp, fresh vegetables, crackers or, best of all, our own Savoury Cheese Biscuits or Savoury Chive Biscuits