A student has a signed flight authorisation from his instructor to fly to the
location where his examiner is waiting for him.
This is a somewhat unusual procedure and one that I wouldn't advocate. No matter how much confidence you might have in your pupil; don't complicate this special day... keep it simple! If the circumstances dictate that both pupil and aeroplane must go to the examiner then have the instructor go with him/her. If your student subsequently failed the Skills Test how would you have recovered the aeroplane back to your operating base without you being with him/her? Notwithstanding all else, have you considered what the examiners thoughts might be with respect to your own (the flight instructors) professional ability/judgement. As an examiner I'd be less than impressed by such a convoluted plan.
TCF