"A relevant body shall maintain an adequate and effective system of internal audit of its accounting records and of its system of internal control in accordance with the proper internal audit practices, and any Office or Member of that body shall, if the body requires (a) make available such documents of the body which relate to its accounting and other records as appear to that body to be necessary for the purpose of the audit and (b) supply the body with such information and explanation as that body considers for that purpose "