Cut the steak into 4-6 even portions and season well with salt and freshly ground black pepper on both sides, then put the steak in a shallow non-metallic dish. Put the remaining ingredients in a small bowl and mix well. Pour the marinade over the steaks, turn to coat, then cover and refrigerate overnight. Remove from the refrigerator 1 hour before cooking to bring the meat back to room temperature.
Preheat a barbecue or chargrill pan until very hot. Remove the meat from the marinade and pat dry on paper towel, then drizzle with a little extra oil and season with extra salt and pepper. Thread two long metal skewers through two of the steaks and repeat with the others. Grill for 3-4 minutes on each side or until cooked to your liking. Rest in a warm place for 10 minutes, then slice and serve with the sauces (recipes on the following page).