Cook the potatoes in lightly salted water until tender, then drain. Let them cool. This can be done well in advance.
Thinly slice the onion. Heat a non-stick pan, add the pancetta, onion, chopped garlic & herbs. Fry for 5-10 minutes until the bacon is crispy and the onion is soft.
Meanwhile halve the potatoes.
Add the potatoes to the pan, stir for a couple of minutes until warmed through. Add the spinach and olives then put a lid on, turn off the heat and let it steam.
When the spinach has wilted, stir through and serve.