Pre-heat your oven to 200C Fan/425F/Gas Mark 7
Cut the tomatoes into quarters and toss them in 1 tbsp of the vegetable oil
Spread them out into a roasting tray, or a baking tray with a lip, and roast for 25 minutes
Meanwhile, put a large soup pot on a low heat and add the remaining vegetable oil. Finely chop the onion, celery and garlic and add to the pot, cook until soft, around 5-10 minutes
Remove the tomatoes from the oven and add them, including all liquid they've released, to the pot
Add all of the other ingredients and simmer the mixture for 10-15 minutes
Use a hand blender to blend the soup until smooth. Or transfer to a food processor and blend until smooth (check if you can add hot liquids to your food processor first as you may need to let the soup cool a little first)
Serve immediately, or allow to cool and store in the fridge in an airtight container for 2-3 days, or in the freezer for up to 3 months