120Joinder of owner or exclusive licensee as a party

120  Joinder of owner or exclusive licensee as a party  (a) an action is brought by the owner of the copyright or by the exclusive licensee; and  (b) the action, in so far as it is brought under section 115 or 115A, relates, in whole or in part, to an infringement in respect of which the owner and the licensee have concurrent rights of action under that section; the owner or licensee, as the case may be, is not entitled, except with the leave of the court, to proceed with the action, in so far as it is brought under that section and relates to that infringement, unless the other party is joined as a plaintiff in the action or added as a defendant.  (2) This section does not affect the granting of an interlocutory injunction on the application of the owner of the copyright or of the exclusive licensee.