1. In a small bowl, mix sour cream, blue cheese, lemon juice, Worcestershire, garlic, and pepper.
2. Stand romaine leaves, tips facing up, snugly in a bowl that is one-half to three-fourths the height of the romaine spears. Trim and discard most of the leaves from radishes, leaving one or two small ones attached. Scatter radishes or cherry tomatoes around lettuce.
3. Serve vegetables and dressing together, so guests can dip lettuce leaves and radishes or cherry tomatoes.