As the Mercedes limousine surged past him at twice the speed limit, the police officer naturally reached for his notebook to issue a ticket.
Unbeknown to him, however, he was about to despatch a fine to his future Fuhrer - one Adolf Hitler.
The long-lost speeding ticket - dated 1931, two years before the Nazi leader became German chancellor - has just been found in a Bavarian archive.
It reveals he was caught at 1.37pm on September 19 in the hamlet of Baar-Ebenhausen on the road towards Munich.
The police officer noted the number plate, IIA 19357, identifying the vehicle as Hitler's personal car.