Bernd Freytag von Loringhoven, 91, is one of the last living eyewitnesses to Hitler's final days.
Hitler's mental health is said to have declined during his final days
He escaped Hitler's bunker just 24 hours before the dictator shot himself.
As an aide to army chiefs he had had daily contact with Hitler.
He describes the order to join his boss Gen Krebs in Hitler's bunker, just over a week before the dictator's suicide, as a death sentence.
He had already survived the fighting on the Russian front and was one of a few to escape from Stalingrad.
He met Hitler for the first time in July 1944. His predecessor had been executed for his part in the bomb plot against Hitler.
The young Maj Freytag von Loringhoven, who was not a Nazi party supporter, says he was "completely flabbergasted" when he saw Hitler just days after the blast.
"I had the image of a very strong, vital person with charisma, but what I saw was a sick old man. His right arm was injured by the attempt and his figure had changed, his head was sunk into his shoulders.
"His left hand was very weak and his left foot dragged behind him."
As for reports that Hitler had had a charismatic spell, he says: "I felt nothing, the eyes were pale and without any expression anymore."
He said he was surprised that Germany was in the hands of such a "sick prematurely old man".
Inside the bunker he describes wild mood swings. There would be a temporary explosion of hope and then confidence would collapse again. The main topic of conversation was suicide - whether they should take cyanide pills or shoot themselves in the head when the Russians arrived.
He also recalls the drunkenness in the bunker, but not the orgies that some accounts speak of. He says he was too busy preparing for situation conferences.
When he met Hitler's mistress Eva Braun - soon to be the Fuhrer's wife - he had no idea who she was. The Nazi elite had been very discreet.
Just days before the end, Magda Goebbels, the wife of Hitler's Propaganda Minister Joseph Goebbels, arrived with her six children.
They would later be poisoned by their parents in the bunker with the help of an SS doctor.
He recalls their pale faces peering out in fear from inside their dark coats.
"When I saw these poor children it pressed my heart," he says.
He feared there was no chance of getting out.
News that his trusted SS Chief Heinrich Himmler had made peace feelers to the Allies had a devastating affect on Hitler in the final days.
"This was like a bomb. Hitler called it treason," the former major says.
But with his work done, just 24 hours before Hitler's suicide, Maj Freytag von Loringhoven was given permission to break out.
He said he had no wish to die "like a rat in the bunker". He took his leave from Hitler with one last meeting which lasted around 20 minutes.
"I personally got the impression that he was a bit envious," he says. "We were 29 or 30 years old and we had a chance to get out because we were sound and young and he had no chance because he was a wreck."
He disputes portrayals of Hitler as raving and foaming at the mouth in the final days.
"I was present at these rages but they were not so excessive," he says.
He never saw him screaming with anger but says he could be "ice cold in his expressions and very aggressive, especially towards the generals".
Hitler was by the end resigned to his fate. His Reich, which was to have lasted 1,000 years, was in ruins.
But looking back, one thing still puzzles him. Hitler, he says, "was still so quiet and realistic just 24 hours before he shot himself".
The young officer escaped, was captured by the western Allies and held as a prisoner of war. He re-joined the army in 1956 and later served Germany in Nato.
He maintains that the divide between the army and the Nazi elite was very real and that although there were rumours, no-one discussed the fate of the Jews in top military circles. It was "taboo" he says.
Asked for his abiding memory of Hitler 60 years on? He pauses at first, then says simply: "He was a terrible creation. Yes, a being, but a being full of evil and cruelty... he was a monster."