Heat a large, heavy-based pan over a medium heat. Add the rashers of streaky bacon and cook for 8–10 minutes, until crisp. Transfer the bacon to a plate lined with kitchen paper and leave about 2 tbsp of the fat in the pan.
Add the chopped onion to the pan and fry for 5–7 minutes, until softened and translucent. Stir in the crushed garlic and cook for a further minute, until fragrant.
Stir in the drained pinto beans, 240ml tomato ketchup, 110g light brown sugar, 2 tbsp yellow mustard, 1 tbsp Worcestershire sauce, 1 tbsp cider vinegar, 1 tsp chilli powder, ½ tsp smoked paprika, ½ tsp salt, ¼ tsp freshly ground black pepper and 120ml water or beef stock. Bring to a gentle simmer, then reduce the heat to low. Cover and cook for 30–60 minutes, stirring occasionally.
Crumble the bacon and stir most of it into the beans, reserving a little for garnish. Taste and adjust the seasoning if necessary. Serve warm.