As the IAS Court pertinently noted, the insurer, asserting lack of timely notice, disclaimed coverage of the additional insureds before the latter had asserted any claims against the primary insured. Therefore, at the time of such disclaimer, the notice given by the primary insured was applicable as well to the additional insureds ( see, National Union Fire Ins. Co. v. Insurance Co., 188 A.D.2d 259, 261, lv denied 81 N.Y.2d 709). Nor does the insurer demonstrate any prejudice attributable to the additional insureds' late notice or other "sound reason" for excusing its performance ( Unigard Sec. Ins. Co. v. North Riv. Ins. Co., 79 N.Y.2d 576, 584). Accordingly, the determinative issue is the timeliness of the notice provided by the primary insured, as to which disclosure is needed.

Concur — Murphy, P.J., Milonas, Wallach, Rubin and Mazzarelli, JJ.