Place the cooked roast pork slices on a large platter or in a baking dish.
Prepare the vegetables: peel and finely dice the red onion; clean and trim the spring onions, cut into thin rings, and set aside; finely dice the pickled cucumbers.
Make the marinade: mix the white wine vinegar with the mustard, salt, pepper and a pinch of sugar. Fold in the red onion and cucumbers. Do not add the rapeseed oil.
Spread the marinade over the roast slices. Cover and refrigerate for 1 hour.
To serve, arrange the roast slices on individual plates. Drizzle with some of the marinade, then drizzle lightly with the rapeseed oil. Sprinkle with the spring onions and fresh herbs.