b'Section 122 and the earlier case law meant that the court did not need to consider further the common law position. It was accepted that any charging decision must be Wednesbury reasonable. It also seems probable that local authorities can only exercise an express statutory power to charge for an activity in order to cover, in broad terms, the cost of that activity. Charging to cross-subsidise another service would be likely to be regarded as a form of stealth tax, and the courts will come down hard on any public authority attempting to raise revenue by taxation where there is no clear power to do so. What is meant by activity or service in this context will depend on the precise wording of the statutory power. Airports 11.3 The sky is the limit (well, almost) for local government trading powers so far as public airports are concerned. Section 12 of the Airports Act 1986 contains definitions of local authority for the purposes of the Act, and includes in relation to England and Wales a local authority within the meaning of the Local Government Act 1972 and the Common Council of the City of London. Principal council means in relation to England and Wales, a council of a non-metropolitan county, other district, or other London borough. Section 24 enables a principal council to enter into an agreement with any associated company (as defined under section 16 of the Act), or with any subsidiary of an associated company, for the provision by the council for that company or (as the case may be) for that subsidiary, of any administrative, professional or technical services. Any agreement under this section should include provision for payment of proper commercial charges in respect of services to be provided under the agreement. Section 25 enables a principal council to make loans to any associated company, or to guarantee loans made to any associated company by any other person for the provision of working capital. Section 25(4) requires such loan to be made on terms, both as to rates of interest and otherwise, no more favourable than the terms on which the council making the loan would itself be able to borrow at the time when the loan is made. There is also a power to provide financial assistance, grants, loans or guarantees for any associated company which has incurred losses affecting the viability of its business. Sections 30 and 31 of the Civil Aviation Act 1982 contain powers enabling a local authority, other than a district council in Scotland, to do one or both of the following: (a)with the consent of the Secretary of State and subject to such conditions as he may impose, establish and maintain aerodromes; (b)make arrangements with the person owning or managing an aerodrome in Great Britain whereby the local authority provide and maintain facilities for civil aviation at that aerodrome; and a district council in Scotland may do as mentioned in para (b), above. 0Such councils mentioned above may, in connection with the establishment and maintenance of aerodromes, provide and maintain roads, approaches, apparatus, equipment and buildings and other accommodation. Section 31 provides: 128'