In a stockpot, crisp the bacon over medium-high heat. Stir in the onion and rosemary and cook until onions are soft and translucent, about 3 minutes.
Stir in chicken stock, potatoes, Worcestershire sauce and cooked chicken. Bring to a gentle boil, and then reduce heat and simmer for about 10 minutes or until the potatoes are tender. Season with salt and pepper to taste and serve hot.