An authority of the State is not required to acquire land under this Division if, before it is required to acquire the land--
(a) in the case of land designated for acquisition as referred to in section 21 (1) (a)--that authority gives the owner of the land written notice that the land is no longer designated by that authority for future acquisition, or
(b) in the case of land designated for acquisition as referred to in section 21 (1) (b)--that authority gives the owner a written undertaking that it will use its best endeavours to remove the relevant reservations and a written notice that the land is no longer designated by that authority for future acquisition.