Wash the mussels under cold running water, removing any beards or obvious dirt. Discard any that are broken or remain open when tapped against the sink.

Finely dice the onion and garlic, slice the carrot and celery, then gently heat the oil in a pot large enough to hold all the mussels in one go. Add all the chopped vegetables to the pot, and cook, stirring, for 5 minutes until softened.

Turn the heat to medium high, add the white wine, tomatoes, oregano, chilli and sugar to the pot, season well with salt and pepper, then allow to cook for a further 5 minutes.

Add the mussels to the pot, cover immediately with a tightly fitting lid and cook for 5 minutes more, giving the pot a good shake from time to time to make sure the mussels cook evenly.

Check after 5 minutes to ensure they have all steamed open, if not cover and let them cook another 2 minutes and check again. When cooked, ladle into warmed bowls, discarding any that remain closed. Tear over some basil or parsley leaves, and serve with plenty of crusty white bread to soak up the rich tomato broth, and a good pungent aïoli or garlic mayonnaise for dipping the bread.