Many years ago with my Dad's 5er. I was driving his Ford V-8 with a manual transmission. Parked the 5er and truck at a RV park office. Put the truck in Neutral and applied the park brake. Was about 10 yard away when I heard someone yell "your truck is rolling". I looked back to see the truck and 5er were rolling backwards down the driveway. Quick thinking park resident ran up, got the door open, jumped in and stopped the truck just before it ran into a lagoon.
Drum Parking brakes only work to stop the truck from rolling forward. They do not work if your nose up on a hill.
No one hurt and no damage, just a couple of lessons learned about park brakes and leaving the transmission in neutral.
