The day before cooking, unwrap the pork and dry the rind really well. Put in the fridge uncovered overnight. Remove the pork from the fridge an hour before you intend to start cooking it.
Heat the oven to 230C/fan 210C/gas 8. Rub 2 tbsp of vegetable oil all over the surface of the pork, including between the scores, and season heavily with sea salt. Put in a roasting tin and in the oven for 30 minutes.
Turn the oven temperature down to 160C/fan 140C/gas 3. Remove the tin from the oven and add the shallots, celery, fennel seeds, rosemary, garlic and white wine to the tin, taking care not to get the rind wet. Put back in the oven for 3 hours.
With 1 hour to go, put the carrots in another roasting tin, toss with 2 tbsp of olive oil, some seasoning and the five-spice, and put in the oven.
If the crackling is still not perfectly crisp after 3 hours, turn the oven up to 230C/fan 210C/gas 8 and roast for another 15-20 minutes until really crisp (remove the carrots if you do this). When done, remove the pork from the oven and wrap the meat, but not the crackling, with foil and rest for 20 minutes. Turn the oven to 220C/fan 200C/gas 7 and continue to cook the carrots, while the meat rests, until they crisp at the edges.
Remove the veg from the pork tin with a slotted spoon and pour off the juices into a jug. Leave for 5 minutes until the fat separates. Spoon out the fat, pour the remaining roasting juices into a pan and simmer gently to make a gravy. Carve the pork and crackling and serve with the carrots, braised veg, gravy and some mashed potato, if you like.