The Grade II listing was established in 2006 and remained accepted for years, enabling much local enthusiasm for renovation of the site and attracting council support. The listing was challenged after a historian accessed the official PLUTO records held at the National Archives. These contemporary records cover virtually every aspect of the PLUTO operation, including regular progress reports. The records provide much detail on the dedicated 3,300 volt mains power supply but make no reference to any power backup facilities at Sandown, Shanklin or Dungeness. A 1943 report on the suitability of the Sandown site noted that Browns generated their own electricity and would thus not detract from the mains power required for the PLUTO motors. The records show 60 American Caterpillar diesel engines were acquired for use throughout the PLUTO project, with no reference to Ruston engines. These and other factors provided the basis for a de-list application.
The advocates of the PLUTO theory support the original basis for the Grade II listing and claim their own subsequent research provides additional evidence to verify the concept. In particular, they say the gauges on the engines show a run time of just 20 days, thus supporting the theory that, not only did the Rustons not exist before 1944, they were not operated thereafter, being exclusively used for PLUTO.
One aspect of the issue that appears to have been overlooked until recently is that the pavilion was still powering Browns' facilities in the 1960s and therefore well within the recollection of many Sandown residents. One resident has responded to a YouTube video of the pavilion:
This was the power station for Browns Ice Cream factory, the Canoe Lake cafe and Golf cafe. I visited it several times in the late 1960s or early 1970s when it was still in use. Your video shows the smaller main generator set, there was a smaller still Lister generator in the middle room, and a larger Ruston set in the other main room. The little Lister allowed the air compressors which started the big engines to build up pressure at the start of the day, before the main engines were started.
I don't believe that this installation had much to do with the PLUTO operation, it pre-dated PLUTO and would have been too small really, around 50kW, to run the fuel pumping station.
It's a shame to see it in this state, it was always very well maintained and clean when in use, but great to see that it's still there! I wonder who owns it now, and if they have any plans for it?
The fact that the Rustons were powering Browns' facilities after the war is not evidence they were doing the same job before the war, but the alternative is to assume the little Lister diesel alone powered everything.
One of the strangest aspects of the issue concerns the serial numbers applied to each of the Ruston engines. Ruston's archives can relate this number to the date the engine was shipped to the customer. It is the definitive evidence. The machine plates have long since gone missing but it was Ruston's normal practice to also stamp the number on the body of the engine. It is a mystery why these numbers have not been investigated.