Preheat the oven to 120°C (100°C fan) and line a large baking tray with greaseproof paper. Wash your tomatoes, remove the stalks and the eye and then cut them all in half. Arrange the tomato halves on the tray, cut side facing up. Drizzle with the olive oil, and sprinkle over the chopped rosemary and thyme, sugar, salt and black pepper. Cook for two hours until the tomatoes have wrinkled and lost about half of their bulk, but are still juicy-looking. Serve straight away or leave to cool on the tray and pop into the fridge until needed.