Bring a small pan of salted water to the boil. Cut the beetroot into small wedges – about the size of orange segments. Simmer in the pan for about 10-15 minutes until tender.
Use a vegetable peeler to cut the carrot into thin strips and put into a bowl with the celery.
Make a dressing by mixing the olive oil with the juice of half the orange and season with salt and pepper.
Cut the other half orange into thin slices.
When the beetroot is cooked, run under cold water to cool it and then add to the bowl, with the other vegetables. Add the orange, walnuts and parsley too.
Pour the dressing over the salad before tossing it and then crumble over the feta to serve.