1.Place barley in a large bowl. Cover with cold water; stand 4 hours or overnight.
2.Heat oil in a large stockpot; cook onion, leek, celery and carrot, stirring, until softened. Add remaining vegetables, stock and water; bring to the boil. Add chicken and drained barley; simmer, loosely covered, about 90 minutes, or until thickened.
3.Just before serving, season soup with salt and pepper and stir in parsley.
