Tie the herbs and bay leaf in a bundle. Heat two thirds of the oil in a pot and cook the onion for 5 minutes without colouring. Add the wine and simmer until reduced by three quarters. Add the tomato, garlic and herb bundle and simmer, covered, for 20 minutes, then uncovered for 40 minutes. Add the mussels and simmer for 5 minutes until they open. Discard any unopened ones.