The day before, pat dry the pork with kitchen paper. In a food processor, whizz together the garlic, paprika, oil and lemon juice with 1 tbsp salt. Rub pork with the marinade and refrigerate for 12-24 hrs.
Heat oven to 150C/130C fan/gas 2. Place potatoes in a large roasting tin and sit the pork on top (the potatoes act as a trivet). Pour over any marinade with 300ml water, cover with foil and cook for 5 hrs.
Remove the foil and increase oven to 180C/160C fan/gas 4. Cook for a further hr.
Remove from the oven and leave to rest for 20-30 mins. To serve, lift off pieces of the crisp skin, then take 2 forks and slowly pull the meat apart. You can cut the pork into hunks if you want but I like it all in stringy bits, ready to go with whatever accompaniments you choose.