| 1. | Cook potatoes until tender. Cool. Peel if desired, then dice. Place in bowl. | 
                            
                                | 2. | Cut onion into quarters and slice thin; add to potatoes along with apple, celery and pickle relish. | 
                            
                                | 3. | In a small bowl, stir together the mayo, mustard, vinegar, and Worcestershire sauce. Spoon over potatoes and gently mix together. | 
                            
                                | 4. | Season with salt and pepper. | 
                            
                                | 5. | Cover and chill for at least two hours or overnight. |