Combine the celery and onion in a slow cooker.
Place the roast on top and season liberally with salt and pepper.
Whisk together the beef broth and Worcestershire sauce then pour it in.
Cover and cook on low heat for 8 hours until the beef is very tender.
Remove the beef to a cutting board and cut into chunks.
Return the beef to the slow cooker and add the beans and chopped butter.
Cover and cook on high for 20 to 30 minutes until the beans are tender.