Make sure the potatoes are all roughly similar in size (cut up larger ones if necessary). Put the potatoes in a saucepan, cover with water, add salt and bring to the boil. Lower the heat and simmer for 8-12 minutes until tender.
Meanwhile, for the vinaigrette, put the cider vinegar, mustard, oil and a little salt and pepper in a screw-topped jar and shake to emulsify.
Drain the potatoes and place in a large bowl. While they are still warm, pour on the vinaigrette and toss to mix. Leave until cold.
Add the capers, gherkins, herbs and some salt and pepper and toss again. Quarter the boiled eggs lengthways, gently mix into the salad and serve.