Wash the potatoes and cook in the skin until cooked. Drain, let cool, peel, cut into slices and place in a bowl.
Wash the cherry tomatoes and cut them in half. Cook the frozen peas in boiling water for 3 minutes and rinse in the colander with cold water. Add to the potatoes with the tomatoes and prawns.
Mix the mayonnaise with lemon juice and 2 tablespoons of water and pour over the salad ingredients. Season with salt and pepper. Mix everything well and let it steep in a cool place for about 2 hours.