Heat the oil in a skillet, add the onion, celery, carrot and garlic.
When they have cooked off a little, add the squid to colour. Add the prawns and toss through. Add the mussels and clams, toss through and raise the heat. Add the parsley, white wine and fish stock. Cook vigorously for 3-4 minutes. Then add the cooked crab meat. Add the pre-made tomato sauce and toss through. Add the cooked spaghetti and serve with a sprinkle of lemon zest and lemon juice.