Heat the stock and saffron to boiling point.
Heat half the olive oil in a paella dish or heavy-based saucepan. Add the chorizo and pancetta and fry until crisp, then remove and set aside. Add the chicken pieces to the pan and fry until golden, remove and set aside with the chorizo.
Add half the remaining olive oil to the pan with the onion, thyme, three-quarters of the garlic, the chilli flakes and red pepper, and cook over a medium heat for 8 minutes or until the onion has softened without colour.
Add the rice, bay leaves and paprika, and stir to coat the rice in the oil, cooking and stirring continuously for 2 minutes. Stir in the white wine, lemon juice and hot stock, and cook for 5 minutes.
Fold in the chorizo mix, the browned chicken, peas, clams and mussels. Put the molluscs in with the edges that will open facing outwards.
Place the dish, uncovered, in a preheated oven 170C/325F/Gas mark 3 and cook for 15-18 minutes. Remove from the oven and leave to rest for 10 minutes. Fold in the butter, tomatoes, parsley and grated lemon rind. Season to taste.
Meanwhile, heat the remaining oil in a frying pan with the remaining garlic and fry the prawns for 2-3 minutes, turning once. For the last minute of cooking, add the squid and fry over fierce heat.
Scatter the prawns and squid over the paella and serve immediately.
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