Less than 10 years ago, I was invited to land at a private strip by someone that wasn’t authorized to give permission for me to do so. I was waved off and did not land or get below 200ft. The person that was actually authorised to give permission took a photo of my aircraft in the air, called CASA and I was staring down the barrel of 50 points penalty. I only got away with it once I gave CASA the name of the person that gave their permission.
It all escalated very quickly and was somewhat stressful. I was guilty until I proved my innocence.
The moral of the story... get permission in writing!