Cook the potatoes in lightly salted water for approx. 15 minutes, until tender. Add the peas for the last 2 minutes of cooking. Drain and put them back into the pan ( cut the potatoes in half, if they are not bite-sized).
Meanwhile, slice the red onion, deseed and finely chop the chilli.
Mix the drained, still hot potatoes with the olive oil and lemon. Season with salt and pepper.
Add the chopped onion and chilli, then the olives. Combine well.
Just before serving, add the feta and mint - toss and serve.