Mix the oil with vinegar, mustard and garlic. Score the meat on both sides, season, then put into a dish. Pour over the balsamic mixture and leave to marinate for 5 mins.
Heat a griddle pan until very hot. Lift the pork from the marinade, scraping off any garlic, then cook for 4 mins on each side. Remove the meat and keep warm. Pour the marinade into the pan with the olives, cook for 2 mins, then stir in the basil. Pour any juices from the pork into the pan, drizzle the sauce over the pork and serve with pasta.