Preheat oven to 190C/375F. Arrange the tomato and pepper halves in a baking tin, cut side up. Drizzle over half the olive oil and then sprinkle the vinegar and thyme on top. Place in oven and roast for 20-25 minutes until softened and lightly charred.
Heat the remaining tablespoon of oil in a pan, add the celery and sweat for 10 minutes until lightly golden, stirring occasionally. Stir in the smoked paprika and cook for 1 minute, stirring continuously. Add the roasted tomatoes and stock and bring to the boil. Reduce the heat and simmer for 10-15 minutes until slightly reduced and then blitz with a hand blender until smooth. Season with a pinch of salt and plenty of pepper, then pass through a sieve for a smooth finish.
When ready to serve, return the smooth soup to a clean pan and reheated gently, stirring occasionally. Do not allow it to boil for too long or it will lose some of its wonderful vibrant colour. To serve, ladle the roast pepper and tomato soup into warmed bowls. Garnish each one with basil sprigs to serve.