In a fine sieve, drain the horseradish of liquid, patting with a paper towel to help release the juices.
In a small bowl, combine the horseradish, sour cream, Worcestershire sauce, vinegar, salt and pepper, tarragon, shallot and garlic. Stir well to combine.
Chill in the fridge for at least an hour (or best overnight) for flavors to intensify.