Heat the oil in a pan and soften the onion and garlic in it. Stir in the carrot, potato and celery and cook for 2-3 minutes. Stir in the vinegar, sugar and salt and add the tomato, tomato purée and herbs. Pour over the water, mix well and bring the liquid to the boil. Reduce the heat, cover, and simmer for 25-30 minutes until the vegetables are tender and the liquid has red