Scrub potatoes well but leave the skins on. Cut into halves, put into a large saucepan and cover with lightly salted water. Bring to the boil, reduce heat and simmer very gently until just cooked through (about 10 minutes). Drain and leave to cool a few minutes.
Meanwhile, in a small bowl, combine the cider vinegar, olive oil, honey, salt and pepper. Whisk to combine. Mix in the saffron infusion. rn
While the potatoes are still slightly warm, cut into 1 cm thick slices and place into a large bowl. Pour over the vinaigrette and gently turn the potatoes until evenly coated. When cooled, cover and set aside for up to 2 hours at room temperature or refrigerate for longer (allow the potatoes to warm to room temperature before mixing the salad).
Preheat a grill and cut the capsicum into 3 or 4 large flat pieces. Place under the grill skin side up and cook until blackened and blistered. Transfer to a bowl and cover with cling film; set aside to cool. Slip off the skins and slice the capsicum thinly.
When ready to serve, add the capsicum, anchovies, shallot and spinach to the potatoes and mix gently. Transfer to a serving bowl, scatter the capers over the salad and drizzle with a little olive oil.