Adolf Hitler was a “sexually confused” serial killer whose violence was driven by lust, according to bestselling German author and psychologist, Volker Elis Pilgrim.

In his new book, Hitler 1 and Hitler 2: The Sexual No-Man’s-Land, Mr Volker claims the Nazi leader had an “orgasm” while watching a film in which Austrian soldiers massacre French troops.

He quotes Marianne Hoppe, an actress who was an acquaintance of Hitler, describing a time that she went to the cinema at the dictator's Berlin palace to watch a film called “The Rebel”.

It featured Austrian troops hurling boulders from a mountain onto the French below.

"Hitler got some kind of thrill and rubbed his knees at this event, as the stones rolled down on the French, and groaned. I don't know if he was crazy, but he got some kind of orgasm," she said. “I wanted to leave during the show. The man was creepy.”

Mr Pilgrim said he had long had a “suspicion that there was a connection between sexuality and violence in Hitler – even more precisely, that it gave him the desire to force men into killing”.

He added: “However, since the ‘lust for killing’ is the decisive feature of serial killers, the question inevitably arises: 'Was Hitler a serial killer who murdered for the purpose of his gratification?'”

A Day That Shook The World: Hitler elected German Chancellor Show all 3 1 /3 A Day That Shook The World: Hitler elected German Chancellor A Day That Shook The World: Hitler elected German Chancellor 30th January 1933: Soldier and statesman President Paul von Beneckendorff und von Hindenburg (1847 - 1934) handing over the rule of Germany to the Nazi leader Adolf Hitler (1889 - 1945). Getty Images A Day That Shook The World: Hitler elected German Chancellor Chancellor Adolf Hitler (1889 - 1945) and Vice Chancellor Franz von Papen (1879 - 1969, centre) on their way to open the first session of the German Reichstag under Nazi rule, 1933. Getty Images A Day That Shook The World: Hitler elected German Chancellor Adolf Hitler (1889 - 1945) and Dr Robert Ley (1890 - 1945) meet a line of workers at a party congress, 1935. Getty Images

"Hitler's...sexuality, I believe, drove the dictator into the most colossal annihilation that man has witnessed," he said.

Mr Pilgrim also speculates about Hitler’s sex life, claiming he abstained from sexual relations with his mistress and then wife, Eva Braun.

He references Hitler’s friend Ernst Hanfstaengl, who described the Nazi leader as being in a “sexual no-man’s-land”. The Fuhrer’s former landlord also said he had inspected the bed sheets and found no indication of sex.