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Peel the tomatoes - prick them with a sharp knife, place in a bowl and cover with boiling water. Leave for a few seconds then drain and cover with cold water. The skins will now come away easily.
Chop the tomatoes and aubergine and seed and chop the peppers. Put in a large heavy-based pan with the onions and garlic and bring to the boil. Cover with a lid, lower the heat and gently simmer for about one hour, stirring occasionally, until tender.
Tip the sugar, vinegar, salt, coriander, paprika and cayenne into the pan and bring to the boil over a medium heat, stirring, until the sugar has dissolved. Continue to boil for 30 minutes or so, until the mixture achieves a chunky chutney consistency and the surplus watery liquid has evaporated. Take care towards the end of the cooking time to continue stirring so that the chutney doesn't catch on the bottom of the pan.
Ladle the chutney into sterilised or dishwasher-clean jars (Kilner jars are ideal) and top with paper jam covers. Seal the jars while still hot. Leave to mature for at least a month in a cool dark place.