Seafood stew

Name: Seafood stew
Ingredients: 1/4 teaspoon saffron threads; 1 tablespoon olive oil; 1 brown onion, finely chopped; 2 garlic cloves, crushed; 1 teaspoon ground paprika; 2 tablespoons thyme leaves; 3 x 400g cans Italian chopped tomatoes; 1 cup fish stock or water; 1 lemon, rind finely grated, juiced; 2 large Desiree potatoes, cut into 2cm cubes; 500g thick white boneless fish, cut into 3cm pieces; 12 mussels, cleaned, beards removed; 12 green prawns, peeled (tails intact), deveined; extra thyme, to serve