Heat oven to 220C/200C fan/gas 7. Put the potatoes in a large pan of water, cover and bring to the boil, then cook for 5 mins until tender. Drain well. Tip the potatoes onto a baking tray, toss in the oil, add some seasoning and cook for 45 mins until golden. Remove from the oven and leave to cool.
Mix the dressing ingredients together in a large bowl. Add the potatoes and toss together to coat. Chill for up to 24 hrs or eat straight away.