As Genghis isn't an instructor, the flight isn't dual, either. As a pilot correctly licensed for the position, and assigned flying duties on the aircraft, but not in command, the candidate is either a co-pilot or ICUS (in command under supervision), and should log the flight as such.
Not in the UK, as its a SPA type the pilot being checked can't log anything I am afraid if Genghis is PIC and not some form of Instructor.