Step 1In a blender, puree the cucumber and yogurt together in batches until smooth. Pour each batch into a large bowl.
Step 2Stir in the garlic, vinegar, salt and pepper. This makes about 6 cups soup.
Step 3Cover and refrigerate several hours or overnight until well chilled.
Step 4To serve, top each serving with slivered radish, a sprinkle of Maldon salt and a few julienne-cut basil leaves.