Where the landlord opposes an application under section 24(1) of this Act on the ground specified in paragraph (f) of section 30(1) of this Act, or makes an application under section 29(2) of this Act on that ground, the court shall not hold that the landlord could not reasonably carry out the demolition, reconstruction or work of construction intended without obtaining possession of the holding if—
For the purposes of subsection (1)(b) of this section a part of a holding shall be deemed to be an economically separate part if, and only if, the aggregate of the rents which, after the completion of the intended work, would be reasonably obtainable on separate lettings of that part and the remainder of the premises affected by or resulting from the work would not be substantially less than the rent which would then be reasonably obtainable on a letting of those premises as a whole.