Peel the garlic cloves, cut in half lengthways and remove the green shoot at the centre. Gently warm the garlic and oil in a large frying pan (big enough to toss the pasta in later). As it starts to colour, take off the heat and let the garlic infuse for 5 minutes, then discard it.
Tip the onion and celery into the garlic scented oil, sprinkle with a little salt and return to a gentle heat. Let them soften, without colouring, for 8-10 minutes. They should sweat rather than fry, so if you hear sizzling add water, a tablespoon at a time.
Add the pancetta and cook for another 6minutes, adding water as before. Stir in the pork and turn the heat up. Don’t colour the meat too much and avoid breaking it up. Add the wine and let it evaporate, then season. Pour in 200ml/7fl oz water, cover and simmer for 20-25 minutes. Mix in a little water if the mixture gets too dry.
While the ragù is cooking, put a pan with plenty of water on to boil. Grate the Parmesan and the zest from the lemon.
When the water is at a rolling boil add 2 tsp salt, then the pasta. Partly cover, bring back to the boil, give it a good stir and reduce the heat so the water boils gently. Taste the pasta 2 minutes before the timing on the packet – remember it will keep cooking while it is tossed with the ragù.
Drain the pasta, reserving some pasta water. Immediately transfer the pasta to the frying pan and toss well over a low heat. Tip in the parmesan and toss well. Add pasta water to dilute, or extra cheese to absorb excess liquid, and mix again.
Toss in the lemon zest and parsley. Serve immediately.