Do not peel the potatoes, but wash them as necessary. If the potatoes are large cut them in half. Boil in salted water for 15-20 minutes until tender
Drain and set aside to cool
Rinse the capers well and mince roughly
Top & tail the radish, then slice thinly
Remove the outer skin from the spring onion, chop off the root (discard) and slice thinly
When the potatoes are cool mix the olive oil, mustard, mustard seeds, lemon juice and capers in a small jug until well combined. Pour over the potatoes
Add the radish & onion. Toss briefly, taste and season as necessary
Just before serving chop the dill and sprinkle over the salad