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.
His report went on: The speed was determined by two officials with two stop watches. The car drove over a measured distance of 200m in 13 seconds, which results in the average speed of 55.3km per hour.
This was double the speed limit and should have resulted in an immediate ban. As it was, a fine was sent to Hitler's Munich flat.
It is not known if Hitler paid the fine, but another document found in the archive, with the word 'settled' stamped on it, revealed the Nazi leader had said his chauffeur Julius Schreck had been at the wheel and he had instructed him "to drive as fast as possible".
It didn't say why.