Place the pork loin in a large bowl.Season with the salt first then sprinkle the cracked pepper all over.With the back of a spoon or spatula spread the Dijon mustard all over the pork top and bottom. (sides do not need to be covered with either salt, pepper or Dijon)Place in a roasting pan or leave in the bowl. Then cover and refrigerate for up to 24 hours (minimum 4 hours)Pre-heat oven to 220°C. When hot place the roast in the oven and cook for 10-15 minutes. Reduce the heat to 160°C and continue to cook the roast until the internal temperature reaches 72°C.
Remove from the oven and let stand in a warm place for at least 15 minutes before slicing and serving.Place on a bed of cooked lentils.