Taking great care, deeply score the pork rind with a sharp pointed knife - the more cuts, the better the crackling.  Even better, ask your butcher to do this for you.

Mix together the lemon zest and juice, olive oil and the Jerk seasoning to make a paste.  Rub the spicy paste over and into the meat (not the rind).  Cover and marinate in a cool place for at least an hour and preferably overnight in the fridge.

Heat the oven to 190'C / 170'C Fan / Gas Mark 5.  Wipe dry the pork rind with absorbent kitchen paper and roast in a large deep roasting tin for 1 hour 30 minutes.  Scatter the sweet potato and onion around the pork, coating in any pan juices and return to the oven for a further 30 minutes or until the potatoes are just tender. 

Lift the pork out onto a platter and leave to rest for 10 minutes before cutting into strips or chunks.  Serve with the roasted vegetables and pan juices skimmed of fat.

Nutritional content per serving, listed ingredients only:
Kcals - 852
Fat (g) - 55
Protein (g) - 50.8
Carbohydrate (g) - 41.9
Sugars (g) - 14
Salt (g) - 0.6