(2) No sum shall be payable by an insurer under sub section (1) in respect of any judgment unless before or after the commencement of the proceedings in which the judgment is given the insurer had notice through the Court of the bringing of the proceedings, or in respect of any judgment so long as execution is stayed thereon pending an appeal; and an insurer to whom notice of the bringing of any such proceedings is so given shall be entitled to be made a party thereto and to defend the action on any of the following grounds, namely (3)Where a certificate of insurance has been issued under sub section (4) of section 95 to the person by whom a policy has been effected, so much of the policy as purports to restrict the insurance of the persons insured thereby by reference to any conditions other than those in clause (b) of subsection (2) shall, as respects such liabilities as are required to be covered by a policy under clause (b) of sub section (1) of section 95, be of no effect : Provided that any sum paid by the insurer in or towards the discharge of any liability of any person which is covered by the policy by virtue only of this sub section shall be recoverable by the insurer from that person.