Scrub the mussels well, remove the beards and scrape off any barnacles. Give the clams a good wash and discard any mussels or clams that are broken or don’t close when tapped. Don’t risk eating a bad one – if you’re not sure, it’s better to throw it away.
Pour the wine into a large pan with a lid and add half the chopped garlic. Bring the wine to the boil, then add the mussels, cover the pan and cook them for 3 minutes until they open. Remove the mussels with a slotted spoon and put them in a bowl, discarding any that don’t open.
Add the clams to the pan and cook, covered, for 2 minutes until they open, then remove with a slotted spoon and add to the mussels. Again, discard any that don’t open. Strain the wine through a fine sieve and set it aside.
Remove the skin of the peppers with a potato peeler, then cut the flesh into thin strips and discard the seeds. Heat the oil in a large flameproof casserole dish or even a wok, add the sliced peppers and onion and allow to soften slowly over a gentle heat. Take your time over this, as it is important for them to be well cooked. Add the strained wine, the saffron and the rest of the garlic. Mix well and bring to a simmer, then turn the heat down.
Add the tomatoes, potatoes, prawns, squid, haddock and lemon peel and enough fish stock to cover. Stir well, cover the pan and cook for 10 minutes over a medium heat until everything is done. Remove the lid and season well with salt and pepper, then fold in the mussels and clams and sprinkle with parsley. Serve at once.