F.2 Development is permitted by Class F subject to the condition that before the end of the period of 24 months from the date when the mining operations have permanently ceased, or any longer period which the mineral planning authority agree in writing—
(a)all buildings, plant, machinery, structures and erections and deposits of minerals or waste permitted by Class F are removed from the land unless the mineral planning authority have otherwise agreed in writing; and
(b)the land is, so far as is practicable, restored to its condition before the development took place or to such condition as may have been agreed in writing between the mineral planning authority and the developer.