T he atmosphere in the bunker on April 20, 1945, Hitler’s 56th birthday, was more funereal than celebratory. There was no trace of the pomp and circumstance of earlier years. The gaunt ruins of the Reich Chancellery were a stark reminder, if one was needed, that there was no cause for celebration. Hitler felt this himself. His birthday with the Russians at the gates of Berlin was an embarrassment to him. He trudged down the assembled line of his staff to receive their murmured birthday greetings with a limp handshake and a vacant expression.

Afterwards, Hitler drank tea in his study with Eva Braun. It was approaching nine o’clock in the morning before he finally went to bed, only to be disturbed almost immediately by General Burgdorf with the news of a Soviet breakthrough and advance towards Cottbus, some 60 miles southeast of Berlin.

After breakfast, playing with his alsatian puppy for a while, and having his valet administer his cocaine eyedrops, he slowly climbed the steps into the Reich Chancellery park. Waiting with raised arms in the Nazi salute were delegations from the Courland army, from the SS-Division “Berlin”, and 20 boys from the Hitler Youth who had distinguished themselves in combat. Was this what Berlin’s defence relied on, one of Hitler’s secretaries wondered? Hitler muttered a few words to them, patted one or two on the cheek, and within minutes left them to carry on the fight against Russian tanks.

By now, most of the leading figures in the Reich — at least those in the Berlin vicinity — were assembled. No one spoke of the looming catastrophe. They all swore their undying loyalty. Everyone noticed that Goering had discarded his resplendent silver-grey uniform with gold-braided epaulettes for khaki — “like an American general”, as one participant at the briefing remarked. Hitler passed no comment.

The imminent assault on Berlin dominated the briefing. The news from the southern rim of the city was catastrophic. Goering pointed out that only a single road to the south was still open; it could be blocked at any moment.

Hitler was pressed from all sides to leave at once for Berchtesgaden. He objected that he could not expect his troops to fight the decisive battle for Berlin if he removed himself to safety. Nevertheless, Hitler seemed indecisive. Increasingly agitated, he declared moments later that he would leave it to fate whether he died in the capital or flew in the last moment to the Obersalzberg.

There was no indecision about Goering. He had sent his wife Emmy and daughter Edda to the safety of the Bavarian mountains more than two months earlier. Half a million marks had been transferred to his account in Berchtesgaden. Goering lost no time at the end of the briefing in seeking a private word with Hitler.

It was urgent that he go to southern Germany, he said, to command the Luftwaffe from there. He needed to leave Berlin that night. Hitler scarcely seemed to notice. He muttered a few words, shook hands absent-mindedly, and the first paladin of the Reich departed, hurriedly and without fanfare. It seemed to Albert Speer, standing a few feet away, to be a parting of ways that symbolised the imminent end of the Third Reich. It was the first of numerous departures. Most of those who had come to proffer their birthday greetings to Hitler and make avowals of their undying loyalty were waiting nervously for the moment when they could hasten from the doomed city.

Convoys of cars were soon heading out of Berlin north, south and west, on any roads still open. Dönitz left for the north, armed with Hitler’s instructions to take over the leadership in the north and continue the struggle. Himmler soon followed. Speer left later that night in the direction of Hamburg without any formal farewell.

Late in the evening, the remaining adjutants, secretaries, and the Führer’s young Austrian diet cook, Constanze Marzialy, gathered in his room for a drink with Hitler and Eva Braun. There was no talk here of the war.

Hitler’s youngest secretary, Traudl Junge, had been shocked to hear him admit for the first time in her presence earlier that day that he no longer believed in victory. He might be ready to go under; her own life, she felt, had barely begun. Once Hitler — early for him — had retired to his room, she was glad to join Eva Braun, and the other bunker “inmates”, even including Bormann and Morell ’s doctor in an “unofficial” party in the old living room on the first floor of Hitler’s apartment in the Reich Chancellery.

In the ghostly surrounds of a room stripped of almost all its former splendour, with the gramophone scratching out the only record they could find — a schmaltzy prewar hit called Red Roses Bring You Happiness — they laughed, danced and drank champagne, trying to enjoy an hour or two of escapism — before a nearby explosion sharply jolted them back to reality.

When Hitler was awakened at 9.30 the following morning, it was to the news that the centre of Berlin was under artillery fire. The dragnet was closing fast. As the day wore on, he seemed like a man at the end of his tether, nerves ragged, under intense strain, close to breaking point.