He (Johannes Fest) was a tall man with strong features; the "telegenic face" (as Wolfgang and I called it) which he displays in most pictures reveals only sternness and determination, without giving any clue to the cheerful character and even happiness that comes when a person is in harmony with himself. One of his friends once said that my father was a rare combination of energy, self-confidence, and mirth. His sharp wit could even turn into high spirits. Friends of my own youth whom I asked for the impression they had of him when they looked back, often said that as children there was hardly another adult whom they so enjoyed being with, because he was able to tell such crazy stories and sing such silly songs. Almost all spoke in these or similar terms of his ability to entertain and his enjoyment of practical jokes. Admittedly, he sometimes suffered from a short temper; that may have been because his good humor did not come from an inner balance alone, but also had something to do with the certainty of being able to deal with all the trials of fate.

It should also be said that my father did not have the least touch of social snobbery and could chat as easily to the girl behind the counter at the baker's as discuss serious affairs of state with a senior civil servant. He was as relaxed with a university teacher as with the children at our birthdays... He liked to laugh and could entertain a company at table all evening with witty anecdotes or - if it was required - more down-to-earth ones.

His origin, life, and strong convictions conferred on my father four qualities, none of which seemed to go with the others and each of which developed an impatience with the other three. He was a republican, a Prussian, a Catholic, and a Bildungsburger. In his case, however, all contradictions were held together by strength of personality and each one of these strands contributed to his intransigence.

One Sunday at the beginning of February 1941, shortly after we had come back from church, two senior Hitler Youth officials entered the building, banging the street door and demanding to speak to my father. They had just found out-one of them shouted from the bottom of the stairs-that none of his three sons had joined either the junior Jungvolk or the Hitler Youth. There had to be an end to it. "Malingering!" barked the other. "Impertinence! How dare you!" Everybody had duties. "You, too!" the first one joined in again.

My father had, meanwhile, gone down to the pair. "Whoever you are," he responded, frowning in annoyance, "I have no intention of allowing you to come here, on a Sunday at that, with a lie. Because we have several times been pestered, likewise on a Sunday morning, by your lads. So you haven't just found out something." And getting ever louder, he finally roared at them, "You accuse me of malingering and are yourself cowards!" And after a few more rebukes he shouted from the second step over their army-style cropped heads, "And now, will you leave my house? Get out! This minute!" The pair seemed speechless at the tone my father dared to use, but before they could reply he drove them back, so to speak, through the entrance lobby and out the door. The commotion had initially startled the whole building, and several tenants had appeared on the stairs. At the sight of the uniforms, however, they quietly closed the doors to their apartments.

Hardly had the street door closed behind the two Hitler Youth leaders when my father raced up the stairs to calm my mother. She was standing in the door as if paralyzed and only said, "This time you've gone too far!" My father put his arm around her and admitted he had forgotten himself for a moment. But first the Nazis had stolen his profession and his income, now they were attacking his sons and Sunday itself One had to show these people that there was a limit. "They know none," said my mother in an expressionless voice. It was all the more important, objected my father, to point it out to them.

To be right when everybody else has been wrong can be a lonely, even disabling experience. This may be a way of understanding the enigmatic character of Joachim Fest, the German historian, journalist and editor who died six years ago. His Berlin family belonged to the Bildungsbürgertum - roughly, the well-educated middle class - and rejected Hitler and National Socialism from the very first moment. They were not part of any resistance group; they did nothing ‘active’ to damage the Nazi dictatorship. They simply refused to let this dirty, vulgar, evil thing across the threshold until, in the final stages of the war, it broke in and took their sons and their father away to defend the collapsing Reich. For their defiance – refusing to join the Hitler Youth or League of German Maidens voluntarily, refusing to abandon their Jewish friends until they ‘disappeared’ - the father lost his job as a headmaster and was banned from all employment. The family was repeatedly threatened by the Gestapo and denounced by its neighbours. They were lucky nothing worse happened to them...

It was the matter of postwar guilt which isolated him. His family was exceptional because it had no reason to apologize for National Socialism, although his father, especially, felt searing shame for his country. Fest clearly found the cult of guilt unconvincing. If you looked more closely, he believed, you could see that the penitent was almost always blaming other people – his neighbours, his nation collectively – and never himself. There was a silent consensus not to stare into the bathroom mirror in the search for causes. The mood was rather: "Yes, we admit that Germany under that criminal regime was guilty; now let’s move on." But Fest, because he was genuinely not guilty, couldn’t play this game. "Unlike the overwhelming majority of Germans, we were not part of some mass conversion … we were excluded from this psychodrama. We had the dubious advantage of remaining exactly who we had always been, and so of once again being the odd ones out." So, too, did quite a few survivors of the sacrificial plots against Hitler. Everyone was respectful to them (unless they had been communists) and gave them medals. But in the Bonn republic they were decorated strangers, with a space around them.

Fest's parents were devout Catholics, proudly Prussian, and had been ardent supporters of the Weimar Republic. Regarding both communists and Nazis with deep distrust, they kept company with like-minded political activists and intellectual Catholic clergy, and had many close Jewish friends.

Great weight was given to learning in this circle, and Fest marks the stages of his formative years by the books he was given to read. At his boarding school in Freiburg, southern Germany, he buried himself in Schiller's Wallenstein "throughout the autumn and early winter of the Russian campaign, so that for me, Freiburg is forever associated with Schiller and as an absurd contrast to the ice storms and blizzards outside Moscow".

Immersed in both high culture and current events, the young Fest was also taken seriously by the adults who passed through his household. This was evidently stimulating for a quick and developing mind, and perhaps also established the intellectual certainty that so marked him out in adulthood. After Fest made clear to his headmaster how parochial he thought him, his fellow pupils asked: "Have you no manners?" "I certainly did, I retorted, but only where there was mutual respect."

The author's bone-dry humour is evident throughout the memoir. It emerges as just one of the many defences the family had to cultivate to endure the Nazi era. They lived with poverty, social exclusion, and under constant threat of visits from the Gestapo, but Fest doesn't take the moral high ground. If ever a book demonstrated the slow but seemingly unstoppable reach of tyranny, even into the private realm, it is this one. He shows how tempting compromise becomes, even while it remains loathsome, and bears witness to the cost and limits of individual courage.

His memories of his father are particularly affecting in this regard. Johannes Fest was a school teacher, whose repeated refusal to join the Nazi party led to him being banned from employment. From 1933 until the end of the war, this intelligent and energetic man was reduced to an observer, watching the gradual erosion of civil society around him, first with incredulity and then with horror. He concentrated his efforts on his immediate circle, urging Jewish friends to leave, and seeing off the Hitler Youth who came calling to forcibly recruit his sons.

Fest absorbed his father's scathing view of the regime, scratching caricatures of Hitler on to his school desk. At the meeting that confirmed his subsequent expulsion, Fest's father put his arms about him – a rare and bravely public show of approbation. His blessing was not easily won. Of Fest's chosen field, his father said the Third Reich was "no more than a gutter subject. Hitler's supporters came from the gutter and that's where they belonged. Historians like myself were giving them a historical dignity to which they were not entitled".

Fest senior learnt of the developing Holocaust through friends, and his sense of impotence must have been intolerable; it certainly left its scars. When his sons entreated him to write about his experiences after the war, he responded: "I did not want to talk about it then, and I do not want to now. It reminds me that there was absolutely nothing I could do with my knowledge." While others accepted requisitioned villas in leafy suburbs from the Allies, Fest senior refused. "For compensation, my father had only the knowledge of meeting his own rigorous principles."

At his father's insistence, Fest did not join the Hitler Youth, but in 1944 volunteered for the army to avoid conscription into the Waffen-SS. Johannes maintained that "one does not volunteer for Hitler's criminal war" and that conscription was preferable; after spending time as a PoW in France, Joachim revisited the subject with his father: "You weren't wrong," the older man allowed him, "But I was the one who was right."

His father's integrity became the standard Fest used to measure the psychological weakness and moral prevarications of his countrymen in a lifelong quest to explain how they could have descended into the madness of the Holocaust. His profiles of prominent Nazis in The Face of the Third Reich (1963), his first success and a groundbreaking work for that time, could have come straight from the pages of Dostoevsky as Fest probes in scintillating style the dysfunctional psyches, personal ambitions, contradictions and self-serving delusions of the men who helped create the Third Reich, while showing how they embodied the attitudes of their classes. Hitler (1973) broke new ground by focusing on a psychological exploration of the Nazi leader who, Fest said, operated like "a reptile", outside established moral norms.