Special grilled marinated Octopus

Ingredients

• 1 whole (about 1.5kg) octopus
• 2 bay leaves
• 1 onion, quartered
• 1 carrot, chopped
• 1 stick celery, chopped
• 1 tbsp black peppercorns
• 250ml extra-virgin olive oil
• 125ml white wine vinegar
• 1 clove garlic, crushed
• 1 tbsp dried oregano, plus a pinch more
• 1/2 lemon
• sea salt flakes