Rub the swordfish steaks with oil and season with salt and pepper.
Make the salad. Cook the beans in a saucepan of lightly salted boiling water for 3 minutes, drain well and refresh under cold water. Pat dry. Place in a bowl and add the walnuts and herbs and a little salt and pepper.
Whisk the dressing ingredients together in a bowl and season with salt and pepper. Drizzle over the salad and toss well.
Cook the swordfish steaks on a hot barbecue for 1—1½ minutes on each side. Wrap loosely in foil and set aside to rest for 3 minutes. Arrange the swordfish on plates, drizzle with the balsamic glaze and serve with the bean salad.