Wash the tomatoes and set aside. In a large saucepan cook the onions, garlic and chilli flakes in about 3 tablespoons of olive oil. Stir in the mustard powder. Stir in the tomatoes Then add the bay leaves, sugar, vinegar and water. Bring to the boil then turn the heat down and simmer for about an hour or boil continuously for less time (say 40 minutes until reduced). When the ingredients have reduced and the chutney coats the back of a spoon it is ready. if the mixture is not reducing and thickening, increase the stove temperature for half an hour until it reduces. Spoon into hot steralised jars, seal. Place the jars in another saucepan with water coming half way up the sides and boil for 15 minutes. Store the jars in a cool, dry place for up to three months or for 10 days in the fridge after opening.