Lord Justice Muskill, Greater London Council (1985) identified four ways in which a decision might be procedurally improper, namely:
- Unfair behaviour towards persons affected by the decision.
- Failure to follow a procedure laid down by legislation.
- Failure properly to marshall the evidence on which the decision should be based. For example, taking into account an immaterial factor or failing to take into account a material factor or failing to take reasonable steps to obtain the relevant information.
- Failure to approach the decision in the right spirit, for example, where the decision maker is actuated by bias or where he is content to let the decision be made by chance.