Pre-heat oven to Gas 6 (400°F/200°C). Cut the fish into chunks. Get the fishmonger to prepare the squid (he just takes out the ink bag and strange innards – if the extraordinary transparent bone is still there you can pull it out). Chop up the squid. Chop up the tomatoes and the pimentos. Peel and chop up the clove of garlic. Put all (except the prawns) in a casserole dish, add the saffron and sprinkle with pepper and salt. Pour over enough chicken stock just to cover. Put the lid on the dish and cook for 1–1½ hours in the centre of the oven. Ten minutes before serving add the unpeeled prawns, the sherry and the herbs. Serve with rice and a green salad.