Where any airport controlled by a principal council, or jointly by two or more principal councils, comes into the ownership of a public airport company as a result of a transfer under section 15(7), any consent given to that council or (as the case may be) to any of those councils under section 30(1)(a) of the 1982 Act, or any consent having effect as if so given, shall (together with any conditions to which it is subject) continue in force so as to enable the council in question, through the company, to maintain that airport; but that council may not by virtue of the consent establish or maintain (whether directly or indirectly) any other airport.