Blanch the peaches in a pan of hot water, and cool them immediately in iced water. Remove the skin, cut the peaches in half, and remove the core. Chop them finely.
Prepare the marinade by mixing the vinegar, olive oil and the lemon juice. Season with salt and pepper.
Finely chop the fish fillet. Lay the slices flat, one after the other in small spoonfuls of marinade. Coat with the rest of the marinade. Cover with thin peach slices. Sprinkle with crushed pink peppercorns and a little dill.
Cover with plastic film and refrigerate for 2 hours before serving.