In oil, cook sausage for 2 minutes over high heat, or until browned. Remove to plate.
Add chicken, and cook for 7-10 minutes over medium heat. Remove to another plate.
Add saffron to chicken stock.
Add onion and garlic to pan and cook for 4 minutes, or until softened.
Add stock, tomatoes, and green pepper. Bring to a boil, breaking tomatoes with a spoon.
Stir in rice, chicken, salt, and pepper. Reduce heat to low, and simmer gently, stirring often, for 20 minutes.
Add peas and sausages.
Peel the shrimp.
Scrub mussels under water and trim beards with scissors. Throw out any mussels that are cracked or do not close when tapped.
Bury mussels and shrimp in the rice. Cook 7-10 minutes, or until the rice is tender, shrimp are pink, and mussels are open. Throw out any mussels that do not open.
Garnish with onions and lemon.