Cut the meat into thin slices. Pound them to tenderize and make them very thin, then set aside.
In a bowl, combine the vegetable oil, olive oil, mustard, vinegar, cumin, salt, paprika, crushed red pepper, black pepper, honey, garlic, onion, and oregano, and mix well.

Place the meat in the bowl with the marinade and mix well. Cover with plastic wrap and refrigerate for at least 10 to 12 hours.
Preheat the oven to 350°F (180°C) with the fan on.
Cut a potato in half and thread it onto 2 skewers. Place them on a baking sheet with the cut side down. The potato will serve as the base to support the gyro. Thread the pork slices onto the skewers one by one.

Cut the tomato into slices, the bell pepper into pieces, and the onion into quarters. Skewer the vegetables on top of the gyro.
Wrap with aluminum foil and bake for 3 hours. Uncover and bake for an additional 30-40 minutes to brown.

Cut around the cooked and browned gyro and set aside. You can return the remaining gyro to the oven to brown the cut areas.
Spread tzatziki on the grilled pitas, add mustard, sliced tomato, sliced onion, parsley, and fries, and serve.