Add the red pepper, chopped tomatoes and 200ml of water. Bring the chilli to a boil then simmer for 20 mins. Tip in the beans and cook for another 10 mins before adding the sweet potato. Season to taste then serve with lime wedges, guac, rice and coriander. Make ahead and freeze for up to 3 months. To make this in a slow cooker:Heat the oil in a large frying pan over a medium heat. Add the onion, carrot and celery. Cook for 8-10 mins, stirring occasionally until soft then crush in the garlic, tip in the sweet potato chunks and cook for 1 min more. Add all the dried spices and tomato puree, cook for a minute then tip the whole lot into a slow cooker. Add the red pepper, chopped tomatoes and beans. Give everything a good stir then cook on low for 5 hrs. Stir in the beans and cook for another 30 mins to 1 hr. Season to taste and serve with lime wedges, guac, rice and coriander.