Heat the oven to 200°C / 400°F. Score the rind into diamond shapes (be careful to cut only the rind, not the meat!) and rub the meat with “Sunday Roast”. Heat the lard or dripping in an ovenproof dish, add the pork bones and cook over a high heat until golden brown on all sides. Add onion, carrots and celeriac. Place the roast rind side down on top of the bones. Add stock and vinegar; make sure the rind is covered with liquid. Roast for about 30 minutes in the oven, then turn and add a little beer. Season the rind with more “Sunday Roast” and return the meat to the oven. Cook for one hour, basting every 10 minutes with beer. Increase the heat to 250°C / 500°F, and roast for another 15 minutes without basting until crisp. Remove from the oven and allow the meat to rest for 10 minutes. Strain the gravy through a fine sieve and cook to reduce a little.