Cook the pasta in plenty of boiling salted water. In the meanwhile, drain the tuna and brake it up. Chop the capers with the well rinsed parsley. Drain the olives and slice them into fine strips.Peel and lightly crush the garlic. Heat the oil in a pan, add the garlic in it and brown briefly then remove it; then add the tomatoes. After simmering for 8 minutes over a high heat, add the tuna, the chopped capers and parsley, the olives and mix; simmer for a few minutes.Drain the pasta al dente and dress it with the sauce. Serve it with a generous sprinkle of ground pepper.