Put a large deep casserole pan on a medium-high heat. Pick and finely chop the rosemary leaves, finely slice the bacon or pancetta, and place it all in the pan with 3 tablespoons of olive oil, stirring regularly, until lightly golden. Stir in the mince, breaking it up with your spoon, and let it brown for 15 minutes, stirring regularly. Peel, finely chop and add the garlic, along with the chopped mixed veg, season with sea salt and black pepper and cook for another 15 minutes, still stirring regularly. Stir in the balsamic, cook away, then add the lentils, juice and all. Add the tomatoes, then half-fill each of the four tins with water, swirl around and pour into the pan. Bring to the boil, then simmer on a medium-low heat for 2 hours, or until thickened, stirring occasionally. Season to perfection, and enjoy as is, batching up extra portions to stash in the fridge or freezer for future meals.