Yes, held the Supreme Court in Clyde & Co v Bates van Winkelhof.
Baroness Hale, giving the leading judgment, held that a member of an LLP (in this case, a fixed-share equity partner of a firm of solicitors) has worker status and thus is entitled to protection against whistleblowing detriments. She stated that "one can effectively be one's own boss and still be a 'worker'", citing the example of a controlling shareholder in a company who is also the chief executive (para 39). She made the point that such a finding is "entirely consistent" with the policy of the whistleblowing laws, and it is "particularly applicable to businesses and professions operating within the tightly regulated fields of financial and legal services." (para 46)
An employment tribunal will now decide the case on its merits. For an excellent analysis of the implications of the decision, see this piece by CM Murray.