Bring a pot of water to the boil. Using tongs, dunk the octopus in and out of the water 3-4 times (helps to make it tender). Then leave the octopus to boil for 20 mins. Peel, chop and parboil the potatoes for about 6-7 mins. When both potatoes and octopus partially cooked, leave to cool a bit
Preheat oven to 200. Mix olive oil, salt, lemon and rosemary together in a small dish. Chop up the octopus and put it in a bowl with the potatoes.
Add the oil mix and mix well. If you have time, leave in the fridge for an hour or so to marinate. When ready, put in an oven proof dish and roast for 25 mins
