Bring the water and salt to the boil in a medium, heavy-based saucepan. Stir in the rice. Reduce the heat to low, cover the saucepan with a tight-fitting lid and simmer for about 20 minutes, or until the liquid is absorbed and the rice is just tender. Remove from the heat. Gently fluff the rice with a fork to separate the grains. Cover with the lid again and stand for 10 minutes, or until the rice is lukewarm.
Whisk the olive oil in a bowl with the red wine vinegar, Dijon mustard and salt and pepper until well combined. Pour the dressing over the warm rice and stir gently with a fork. Set the rice aside to cool completely.
Bring a small saucepan of salted water to the boil. Add the peas and cook until they are bright green and tender. Drain the peas and refresh them under cold running water. Pat dry with paper towels.
Spoon the rice into a serving bowl. Add the peas, ham, spring onion, radish, celery, mint and parsley and mix until the vegetables are evenly distributed. Fold in the mayonnaise and season to taste with salt and pepper. Sprinkle with the chives just before serving.