I had the belt drive adjusted today. The squealing noise has now gone under all levels of load. The belt was out of alignment which caused the noise. Hopefully this will be useful for people who have the same noise on their Super 3s.
Great news! Did it need to be done by your dealership/factory? Is it something I can check myself or ask my mechanic to do for me?
I purchased mine from Morgan Works at the Factory. The service department is at the same location as the Factory so whilst separate I guess has easy access to the people at the Factory as they are all part of the same complex and know each other / work with each other.