56.—(1) In every suit or proceeding, the court may have regard to the estate duty that may be payable on property passing on the death of any person and may, if the court considers it necessary for securing the payment of any estate duty, cause notice to be served on the Commissioner.
(2) The Commissioner may thereupon or at any time thereafter intervene in such suit or proceeding and may with leave of the court be joined as a party thereto.
(3) The Commissioner may of his own motion intervene and be heard, either personally or by counsel in any pending suit or proceeding by which the right to claim or receive estate duty is or is likely to be affected.
(4) The costs of or occasioned by the intervention of the Commissioner shall be in the discretion of the court.