E.4 Development falls within this paragraph if—E+W
(a)it is urgently required for the efficient running of the airbase; and
(b)it consists of the carrying out of works, or the erection or construction of a structure or of an ancillary building, or the placing on land of equipment, and the works, structure, building, or equipment do not exceed 4 metres in height or 200 cubic metres in capacity.