The broker, prior to the effective date of the policy, shall deliver written notice to the prospective insured disclosing the relationship between the broker and the controlled insurer; except that, if the business is placed through a subbroker who is not a controlling broker, the controlling broker shall retain in his records a signed commitment from the subbroker that the subbroker is aware of the relationship between the insurer and the broker and that the subbroker has or will notify the insured.