1.Cook potato and beans separately in boiling water until just tender. Drain well. Transfer potato and beans to a large bowl. Add tomato, olives, egg and lettuce. Set aside.
2.Meanwhile, combine flours with salt and pepper in a shallow dish. Toss fish lightly in flour mixture, shaking oil excess. Pour oil into a large frying pan to 1cm deep. Heat over moderately high heat (oil is ready when a cube of bread crisps quickly without absorbing it). Shallow-fry fish, in 2 batches, for 2 minutes each side or until golden and cooked. Drain on paper towels.
3.Drizzle dressing over salad. Serve fish with salad and lemon wedges.