Medical documents uncovered in a Bavarian archive appear to prove once and for all that Nazi dictator Adolf Hitler did only have one ball, finally confirming the lyrics to a popular war time ditty.

German tabloid Bild reports that University of Erlangen historian and archivist Peter Fleischmann found a medical assessment that Hitler had to undergo in 1923 following his botched Beer Hall Putsch. In it, medical officer Dr Josef Brinsteiner recorded that Hitler, who was locked up in Landsberg prison, suffered from "right-side cryptorchidism" or an undescended right testicle.

He described Hitler's general health condition as "strong and healthy". The future dictator, then artist and writer, weighed 78kg.

Men's testicles descend from inside the body into the scrotum during childhood. But in some cases one or both fail to descend, causing the testicle to go into atrophy.

The anti-Nazi song mocking Hitler and other Nazi leaders was sung by generations of British schoolchildren, inspired by their parents or grandparents.

The popular song begins: "Hitler has only got one ball, the other is in the Albert Hall".

It was reportedly written by a publicist for the British Council in 1939 and continued: "Hitler has only got one ball. Göring has two but they are small. Himmler has something similar. And Goebbels has no balls at all."

In 2008, a document of a conversation in 1960 between German war doctor Johan Jambor and his priest seemed to confirm Hitler's medical condition but gave an alternative explanation. According to the priest's document, Hitler lost a testicle during the Battle of the Somme in 1916 where he was in the trenches.