To cook the octopus
Rub the salt into the octopus, rinse well under running water. Bring the water and vinegar to the boil along with the onion and bay leaf. Add the octopus, leave to infuse just below the boil for approx. 1½ hrs. Remove, allow to cool slightly. Rub off the skin with paper towels.
To fry the octopus
Cut the octopus into approx. 4 cm pieces. Heat the oil in a non-stick frying pan. Brown the octopus in batches for approx. 8 mins. per batch, remove from the heat, season.
Cook the potatoes in boiling salted water for approx. 10 mins. until just soft, drain. Mix the lemon juice, oil and salt in a bowl. Add the octopus and potatoes along with all the remaining ingredients, mix.