On 8 January 2016, a Bombardier CRJ200 crew were suddenly presented with a failure of one of the two main PFDs and a consequent uncommanded Autopilot disconnection during the cruise in dark night VMC conditions. No attempt was made to identify the failure as a single system fault and to maintain control using the second serviceable main PFD - which had the same indications as the Standby Horizon. Control of the aircraft was lost beyond possible recovery with terrain impact occurring 80 seconds after the initial appearance of erroneous PFD indications which were attributed to malfunction of the corresponding IRU.