Boat Yard near Medley Bridge

While out and about in Port Meadow, close to the boat yard on Port Meadow, I come across this stone with a very nice Oxford Preservation Trust Award 1992 on top of it. I would think it was for the keeping of the Boat Yard, but it did not say why the award was given. I had a look at the Trusts website, but could not find anything, this will be another one of those things to look up and get back to you on.