In a cast iron Dutch oven, heat vegetable oil. Add half the beef and allow it to brown for 6 to 7 minutes. Remove and repeat with the other half of the beef.
Add onion, celery, and carrots. Stir fry for 3 minutes. Then add garlic and continue to stir fry for 30 seconds.
Return browned beef to the Dutch oven. Add Marmite and diced tomatoes.
Add water. Cover and bring to a boil. Reduce heat to low and simmer for 1½ hours.
Add potatoes, salt, and pepper.
Continue to cook for another 15 minutes or until sauce thickens. Turn off stove.