The primary insured's forwarding of the summons and complaint in the underlying personal injury action to its carrier, Sirius, constituted timely notice to Sirius of the claim involving the additional insured, since the interests of the named insured were not adverse to the interests of the additional insured ( see New York Tel. Co. v Travelers Cos. Sur. Co. of Am., 280 AD2d 268). Sirius' lengthy delays in disclaiming coverage, after it knew or should have known of the purported bases for disclaiming coverage based upon exclusions in its commercial general liability policy, were unreasonable as a matter of law, and thus ineffective ( see Insurance Law § 3420 [d]).