Potato and radish salad

Ingredients

• 2kg waxy new potatoes, such as charlottes, halved if large
• 2 bunches of radishes, trimmed and finely sliced
• Bunch of spring onions, finely sliced
• 2 punnets mustard cress, trimmed

For the dressing

• 5cm piece fresh horseradish, finely grated, or 2 tbsp horseradish cream
• Juice of ½ lemon
• 4 tbsp olive oil
• 2 tbsp mayonnaise