The architect of Porsche's winning trade on Volkswagen shares is not an investment banker but a stubble-chinned manager from rural Rhineland-Palatinate whose previous biggest experience was to be finance director of a floor coverings company.

Holger Härter, the chief financial officer of Porsche, certainly has an atypical career for somebody who is now earning the German sports carmaker billions of euros from derivatives. But his role has inspired VW investors and analysts to simultaneous bouts of admiration and despair.