Obtaining Consent Each subject will be given an information sheet describing the study procedures, offered the opportunity to ask any questions and must sign that they have understood the contents. A separate consent form will be signed by the participant. Any questions will be dealt with by an investigator. The headache diary and all information to be read by subjects will be designed to have a Flesch Kincaid reading age of less than or equal to grade 8. Subjects will be free to withdraw from the trial at any stage.