An application under the slip rule may be made informally (e.g. by letter) or formally, by application under Part 23 (as to which see Section 20). The application may be dealt with without a hearing if the applicant so requests, or with the consent of all parties, or where the court does not consider that a hearing would be appropriate. However, if the application is, or is likely to be, opposed, it should be listed for hearing before a Costs Judge.