1. Slice the bread and soak in cold water for a few minutes. When the bread is soaked through drain the water, squeeze out any excess water and break it up into small pieces. Place the tomatoes, onion, radishes and celery in a large mixing bowl and add the basil. Toss and add the bread.
2. Season to taste with salt and pepper and drizzle over the red wine vinegar and then the oil. Toss to coat.
3. Crumble in the tuna and mix well. Garnish with basil leaves and serve.
