Boil jacket potatoes and peel them (not necessary for new potatoes or triplets).
Halve the cucumber lengthways and scrape out the seeds with a teaspoon. Cut the cucumber into small cubes. Mix a sauce / paste from mustard, lemon juice, oil, dill, pepper and salt. Mix with cucumber and egg cubes and let steep for 30 minutes. The paste will then be thinned by the cucumber juice that escapes.