Put the potatoes in to a pan of boiling water and simmer for 10 minutes.
Drain and put in to a dish with the olive oil and mix well. Put the potatoes in to a preheated oven at 200°C/400°F/Gas 6 for 25 minutes.
When cooked, pour in to a large bowl and add the creme fraiche, lemon juice and zest, watercress, roasted peppers and salt and pepper and mix well.
Transfer on to a serving dish and sprinkle with fresh dill.
You can easily make this a vegan potato salad by using vegan creme fraiche (we like Oatly). You could of course use vegan mayo, but I think the vegan creme fraiche tastes much better than a mayo alternative. It's fresher.
If you want to make this a little more indulgent, but with a lot of extra flavour, try adding chopped up cooked bacon. Bacon in potato salad is truly something special.
This salad is best served still a little warm. The warm potatoes will wilt the watercress a little too.