Heat the oven to 140C/fan 120C/gas 2. Heat 2 tbsp olive oil in a large solid casserole. Add the pork and cook until crisp and golden. Add the onions and cook until soft, then add the garlic and cook for a further minute. Add the mustard, sugar, treacle, smoked paprika, cumin, tomato purée, tamarind paste and chopped tomatoes to the pan, stir well and cook for 30 seconds. Add the beans and 600ml of the cooking liquid, the bay leaves and thyme. Mix well, bring to the boil and cover with a tight-fitting lid. Cook in the oven for 3 hours until the beans are tender and the sauce thickened. Serve in bowls with a spoon and crusty bread.