Just read the report. Sounds like someone flying VFR in very poor destination weather. Control of the aircraft was lost with large pitch up and pitch down maneuvers ending up in a final stall and spin. The possible initiating factor(which could not be conclusively established) was that an attempt was made to make a significant pitch control input, resulting in the trim operating in the opposite direction to maintain altitude, resulting in a significant out of trim situation in IMC.
Regardless of whether this was what actually happened, a good reminder on what can happen when trying to override the autopilot on some aircraft......
Piper_PA-46-350P_Malibu_Mirage_N186CB_11-16.pdf (publishing.service.gov.uk)