Where in accordance with section 136 of this Act land had an original unexpended balance of established development value, and at any time on or after the appointed day (whether before or after the commencement of this Act) any new development of that land is or was initiated, then (subject to the following provisions of this section) for the purpose of determining whether that land or any part thereof has or had an unexpended balance of established development value at any subsequent time—
shall be deducted from the original unexpended balance of established development value of that land, and the original unexpended balance of that land or that part thereof shall be treated as having been reduced or extinguished accordingly immediately before that subsequent time.
Subsection (1) of this section shall not apply to any land if, in respect of any interest therein, a payment has become or becomes payable under section 59 of the Act of 1947 (which provided for payments in respect of certain war-damaged land).
For the purposes of subsection (1) of this section no account shall be taken of any development initiated before 1st January 1955, if—