Preheat the oven to Gas Mark 4, 180°C (350°F).
Heat the oil in a large ovenproof saucepan. Add the pork in 2 batches and brown on all sides.
Set the pork aside. Add the onion and garlic to the pan and cook for 3-4 minutes. Then add the coriander, cumin, smoked paprika and cook for a further minute or two. Then stir through the tomato purée. Return the pork, add the tomatoes, stock, sugar and salt and pepper. Bring to a simmer, cover with a lid and place in the oven, cook for 1½ hours or until the meat is tender.
While the pork is cooking place the potatoes in a saucepan, cover with cold water and boil until soft. Drain, then add the milk, butter and salt and pepper and mash until creamy.
When the pork is cooked remove it from the oven and set aside to cool slightly. Shred the meat with 2 forks and place the shredded pork and sauce in a deep ovenproof dish, approximately 34cm x 27cm. Add the kidney beans and mix to combine. Spoon the mashed potatoes over the pork mixture and place in the oven. Cook for 30 minutes or until golden brown.