Jon has talked about the pannage pork from the New Forest but you don’t have to use that for this recipe, just make sure to buy the best free-range pork you can get. A reasonable amount of fat is a good sign and the meat should be fairly dry and firm.
Brining meat gets the flavours right into the muscle and also helps to make for more succulent eating. The science bit is that a 5.5 per cent brine solution partially dissolves some of the protein structure and increases the amount of water the muscle cells can hold. The water that flows from the brine into the cells also contains salt and any flavourings in the brine. The meat still loses moisture when cooked but this is partly offset by the extra it has absorbed from the brine. If the science of cooking fascinates you, then Harold McGee’s On Food and Cooking is well worth adding to the book collection.