Which of these is the only element that is not compulsory to include on your daily log?

The only element not compulsory to include on your daily log is the number on your driver's licence. While keeping a daily log entails documenting various aspects of your driving duties and vehicle usage for compliance and safety, certain details are explicitly required and specified by regulations.

The odometer reading at the start of the day is essential because it helps to track mileage and ensures that vehicles are maintained properly, contributing to safety and regulatory compliance. The location at which your duty status has changed is also important, as it indicates when and where you may switch between different types of driving statuses, which is crucial for monitoring hours of service.

The number plate of all buses driven that day is required so that there's a clear audit trail of which vehicles were in use, aligning with safety checks and accountability.

In contrast, while knowing your driver's licence number is important for identification and regulatory purposes, it does not directly relate to the operational details of your daily driving log. Therefore, including it in the log is not a requirement, making it the correct answer for what is not compulsory in a daily driving log.