Heat a large non-stick frying pan over a medium heat. Add the beef mince and cook for about 10 minutes, breaking it up, until evenly browned. No oil is needed as the mince releases enough fat.
Transfer the browned mince to the slow cooker.
In the same frying pan, heat the olive oil. Add the onion, celeriac and red pepper and cook for about 10 minutes, until softened.
Add the garlic, cumin, smoked paprika, paprika and chilli powder. Fry for 1 minute until fragrant.
Tip the vegetable and spice mixture into the slow cooker.
Pour about half of the beef stock into the frying pan, scraping up any leftover spices and flavours. Tip this into the slow cooker, then add the remaining stock.
Stir in the dried oregano, tomato purée, chopped tomatoes and Worcestershire sauce. Season with salt and black pepper.
Cover and cook on medium for 6 hours.
Halfway through cooking, stir in the kidney beans.
About 20 minutes before the end of cooking, stir in the brown sugar.
Taste and adjust seasoning if needed. Serve hot, topped with fresh coriander.