Boil the kettle. Score the fat on the uncooked joint with a sharp knife, then pour boiling water all over the fat. Dry it thoroughly with a kitchen towel. Then roast the joint in the oven as normal.
PS - for fab roast potatoes, boil some new potatoes in their skins for 10 minutes, then put them into the same roasting tin as the pork when there are 20 minutes left to go. The potatoes will then roast in the pork fat.
Take crackling off joint and rub with salt. Put on trivet in roasting dish and cook in over at 200 (gas 7-8) for as long as it takes. Make sure you pour out the fat that collects in the bottom of the dish as that will burn and then burst into flames.....