Drain and rinse the beans.
Chop the parsley, scallions and celery and place in a bowl with the beans.
Chop the sundried tomatoes and red pepper, and add those to the salad with the capers.
Mix the olive oil and cider vinegar in a bowl with the mustard until combined and pour over the salad.
Stir the three bean salad well and season with sea salt and black pepper.