Preheat your oven to full whack, it needs to be at least 220°C/425°F/gas mark 7.
Place your pork on a clean work surface, skin-side upwards. Get yourself a small sharp knife and make scores about a centimeter apart through the skin into the fat, but not so deep that you cut into the meat.
Rub salt right into all the scores you’ve just made, pulling the skin apart a little if you have to. Brush any excess salt off the surface of the skin and turn it over. Season the underside of the meat with a little more salt and a little black pepper. Place your pork, skin side-up, in a roasting tray big enough to hold the pork and the vegetables, and place in the hot oven.
Roast for about half an hour until the skin of the pork has started to puff up and you can see it turning into crackling. Turn the heat down to 180°C/350°F/gas mark 4 and roast for another hour. Take out of the oven and baste with the fat in the bottom of the tray.
Carefully lift the pork up and transfer to a chopping board. Add all the veg, garlic and thyme to the tray and stir them into the fat. Place the pork on top of everything and pop the tray back in the oven. Roast for another hour. By this time the meat should be meltingly soft and tender. Carefully move the meat to a serving dish, cover with tin foil and leave to rest while you make your gravy.
Spoon away any fat in the tray, then add the water or stock and place the tray on the hob. Bring to the boil and simmer for a few minutes, stirring constantly with a wooden spoon to scrape up all those lovely sticky tasty bits on the bottom of the tray. When you’ve got a nice, dark gravy, pour it through a sieve into a bowl or gravy boat, using your spoon to really push all the goodness of the veg through the sieve. Add a little more salt and pepper if it needs it.
Serve the pork with the crackling, gravy, some creamy mashed potato, nice fresh greens and a dollop of English mustard.