Heat saucepan with tight fitting lid, on medium heat. Add oil, onions, garlic and chilli; cook for 1 minute.
Add mussels, wine, and replace lid; cook 2 minutes on high heat. Add tomatoes and lemon; stir to promote even cooking. Replace lid and cook 2 minutes on high heat then add spring onions.
When shells open, the mussels are ready. Serve in large bowl, accompanied by a finger bowl.