Cook the potatoes in a saucepan of boiling water until soft – this will take about 15 minutes. Drain and set aside.
Mix the cherry tomatoes and rollmops together. Combine the mayonnaise, horseradish sauce, zest and juice of lemon, dill, capers and season well.
Stir the potatoes into the tomato and rollmops and coat with the mayonnaise mixture. Transfer to a salad bowl. To serve, garnish with sprigs of dill and slices of lemon.
*Some Kosher products may only be available in limited stores.