Place the herring in a shallow dish and sprinkle over the dill and capers. Pour the vinegar and sugar in a pan and bring to a vigorous boil, pour over the herring and cling film immediately. Leave to cool for at least 30 minutes (overnight is the best).
To make the dressing, add all the ingredients into a bowl and season to taste.
To build the salad, place the chicory leaves onto a plate, add the apple batons, then the beetroot and potatoes. Take the cling film off the herring and place the fish on the salad. Finish with a generous spoon of the dressing.