1.Remove and discard prawn heads. Cut prawns lengthways, three-quarters of the way through and down to 1cm (½ inch) before the tail, leaving shells intact; press prawns down on board to flatten.
2.Combine prawns, rind, chilli, garlic, oregano and half the oil in medium bowl. Cover; refrigerate 1 hour.
3.Wrap a prosciutto slice firmly around each sardine.
4.Cook octopus and squid on heated oiled grill plate (or grill or barbecue). Combine octopus and squid in medium heatproof bowl with remaining oil, vinegar and 2 tablespoons of the parsley. Cover to keep warm.
5.Cook prawns and sardines on heated oiled grill plate (or grill or barbecue).
6.Meanwhile, cook mussels, covered, on heated oiled flat plate about 5 minutes or until mussels open. Place mussels in medium heatproof bowl; drizzle with juice, sprinkle with tomato and remaining parsley. Serve seafood with lemon wedges, if you like.
You can buy butterflied sardines from most good fish markets, or get your fishmonger to butterfly the fish for you. To butterfly your own fish, buy an already gutted fish, slice down the length of the belly until just before the tail, place fish, belly-down, on a chopping board and roll gently with a rolling pin several times to flatten, pull head gently up and away towards the tail, removing head and bones together.