The discretionary powers of the Greater London Council were limited by implied fiduciary duties and undertakings to run London Transport on business principles.

The claimant renewed his TV licence early to avoid an increase in the licence fee. His TV licence was revoked. The Home Secretary said that he was entitled to revoke TV licences under s 1(4) Wireless Telegraphy Act 1949. The claimant sought a declaration that the revocation of his TV licence was unlawful.

A public body must exercise a discretionary power for the purpose for which it is granted. If a statute states the purposes for which discretion is to be exercised, the courts will treat the stated purposes as exhaustive. If the power is exercised for any other purpose the public body’s action or decision will be ultra vires.

The Home Secretary took into account public opinion and his own policies and ignored the statutory requirement to consider the welfare of the child when setting tariffs of youth custody.

A public body must take into account relevant matters and discard anything irrelevant. Where the relevant considerations are expressly stated in a statute any deviation will make a decision invalid.

The Court of Appeal had to consider whether it was lawful to confirm a slum clearance compulsory purchase order when one of the buildings was fit for human habitation according to an inspector’s report.

A public body must base its conclusions of fact on the evidence before it. A public body’s decision can be challenged by judicial review on the ground that it has ignored relevant evidence, or has misinterpreted evidence or has unreasonably made a decision which is contrary to the weight of the evidence presented to it during the decision-making process.

The House of Lords had to decide whether the minister’s policy concerning awarding grants of financial assistance was lawful.

When a public body is given a discretionary power it is entitled to formulate and adopt a policy governing its decision-making process. But it cannot adopt a policy which prevents it exercising its discretion by shutting its ears to certain types of application. It must be prepared to consider every application on its merits. Whether there are any special circumstances justifying departure from its usual policy.