There is no such formal requirement. From Standards Document 3 Version 6 (Guide to the CPL Skill Test):
3.6.5 The En-Route Procedures (Section 3)
Section 3 is usually flown after Departure to ensure an efficient flow to the flight. During this section of the flight the aeroplane is assumed to be on a passenger carrying operation under Visual Flight Rules. When the aeroplane has achieved cruising altitude, normal cruising speed and is on heading for the first destination, the applicant should confirm to the Examiner the heading, altitude, and ETA, thereafter advising any changes. For example, "2 minutes late at my halfway point - the revised ETA is now. . ." Corrections to heading or ETA shall be calculated rather than based on track crawling, impulse or inspiration. The applicant is expected to navigate by visual positioning in a practical way, not to feature crawl. Numerous heading or altitude changes that are the result of poor flying may constitute a fail in this section. The applicant is expected to make changes to his heading and ETA in order to correct deviations from his plan. Radio navigation aids may not be used during the first leg of the en-route section although they may be tuned and identified in anticipation of their use later in the flight.
3.6.6 At or before the first destination the applicant will be instructed to carry out a diversion to an alternative destination or airfield. This is not an emergency procedure. A prominent alternative destination or airfield will be pinpointed on the applicant’s chart. The applicant may be asked to commence the diversion at or before the original destination. The applicant should nominate his heading, altitude and ETA for the diversion and again use recognised techniques and visual positioning to navigate to the second destination.
3.6.7 During the diversion leg the applicant may supplement visual navigation techniques with the use of VDF, VOR, NDB, DME and/or GPS information. Only GPS raw data (latitude and longitude or range and bearing from a waypoint) may be used. GPS map displays or “GOTO” facilities will not be permitted. The examiner will deny the use of any aid that would allow the applicant to track directly to the diversion destination. If navigation aids are used, the applicant will be assessed on their correct use.
3.6.8 Demonstration of radio aid tracking in VMC will be required at some stage; the Examiner will decide when to ask for this exercise to ensure efficient use of time and airspace. He will nominate the facility to be used and the track to be intercepted and maintained. As this item requires the demonstration of satisfactory skill in heading selection and drift assessment, it must be completed using an RMI, RBI, HSI or CDI display. This is a visual flying exercise using radio aids to assist navigation.