1. Boil the potatoes in 2 cups of water in a deep kettle. Cover and cook over moderate heat for about 20 minutes, until the potatoes are tender.
2. When thoroughly cool, dice potatoes and place in a big bowl.
3. Add diced beets and mix with the potatoes.
4. Set aside 1/4 cup of peas for garnishing and add the rest to the bowl.
5. Save 1 egg to use as a garnish. Chop the rest and add to the bowl.
6. Peel the skin off the apple and remove the core. Cut the apple into small pieces, place in a small bowl and sprinkle with lemon juice. Add apple to the salad.
7. Add the vinegar, olive oil and sugar.
8. Mix thoroughly. Chill and serve.