For the dressing:combine the yoghurt, lemon juice and salt and pepper and mix well.
Put the diced apple, radish, celery, lettuce, half the amount of walnuts and the yoghurt dressing in a large bowl and fold in until everything is coated well with the yoghurt dressing
Serve with the shredded chicken on top.
You can always add a little lemon pepper seasoning to the yogurt dressing in place of the salt and pepper.
Can be served without chicken and if you are vegan just replace the yogurt with some soy yogurt :)