2Interests of colliery concerns and of class A subsidiaries thereof in fixed and movable property used for colliery activities, coal carbonisation and coal products distillation activities allied with colliery activities, or manufactured fuel activities (in this Act referred to as " colliery production activities ") :
Provided that where a colliery concern or a subsidiary thereof, or a concern of which a colliery concern is a subsidiary, operates iron and steel works at the primary vesting date—
(a)interests of the colliery concern or of a subsidiary thereof in fixed and movable property used for coal carbonisation and coal products distillation activities allied with colliery activities shall be excepted from this paragraph so as to fall instead within paragraph 21 of this Schedule ; and
(b)the activities for which that property is used shall not be treated as colliery production activities by virtue of this paragraph, but without prejudice to the provisions of the said paragraph 21.