(1) Notwithstanding any enactment or rule of law but subject to this section, the Board is hereby authorised to amend, on or before the 31st day of March 1993, any trust deed in respect of any existing scheme in order to:
(4) Subject to subsection (2) of this section, where a trust deed has been amended in accordance with this section, any payments made by the Board and any action taken by the Board before the amendment was made that would, if the terms and conditions applying to the scheme or the terms and conditions of the trust deed for the scheme, as the case may be, were the same as those contained in the trust deed as amended, have been valid, shall be deemed to be and always to have been valid.