Chop up the tomatoes, carrots, onion, swede and potatoes. Place in a medium pot together with a stock cube, add in 1.5l of water and simmer for around 15 minutes or until the vegetables are tender.
Blend with an immersion blender or transfer to a food processor in batches and blend until smooth.
Stir in the chopped tomatoes, tomato pure and chilli flakes, and let it simmer for further 10-15 minutes. Season with salt and pepper, taste and check the seasoning, then serve.