Sir Peter de la Billiere, General

It's the quality of the ingredients that counts:

Find a Butcher or Farmers' Market where you can obtain genuine home produced, naturally reared pork from a free range herd. Select a fresh joint on the bone, say 2 ½ kgs, with good firm skin and a distinct, but not excessive, layer of fat under it: this ensures a succulent joint with good crackling and heaps of flavour. The texture of the meat will be firm, not flabby like so much imported or supermarket pork. This is because of the healthy active life of the pig, even though such pigs will probably have been penned in straw yards for their final weeks. Ensure the butcher has scored the skin in fine strips.

Place the joint in a roasting tin and rub the skin with salt.
If AGA cooking, there is no need to add more than a minimum of lard or oil, if any. Add as necessary for conventional cookers.
Place joint in hot oven 220°C, Gas Mark 7 , for 25mins to the ½ Kilo plus 25mins over. (My wife does this by guesswork, roughly 20mins to the ½ Kilo etc., then judges whether it needs longer). The meat must be fully cooked through but it will shrink and spoil if over cooked. Allow to rest for 10mins or so in warm oven before serving.
Cook roast potatoes separately, the steam - if round the joint - can spoil the crackling. Serve with a rich brown gravy, apple sauce and a suitable green vegetable.