For his part, Josef Mengele awaited his son’s visit to his hideout in a suburb of Sao Paulo with much anticipation, prepared for the only inquisition in his life. “You wish to have a dialogue,” he wrote to Rolf. “Very well…”

The omens were not promising. In one letter, Mengele told his son: “I do not have the minutest inner desire to justify, or even excuse, any decisions, actions or behaviour regarding my life….my tolerance has its limits.”

Nonetheless, Mengele, now 65 and with little to do except fret about his health, his finances, and post-war Germany, urged Rolf to make his stay a lengthy one. It was not “easy for me to express how much I look forward to that meeting” he wrote.

Mengele’s instructions to the family’s trusted go-between, Hans Sedlmeier, and to Rolf about the secret visit resembled a set of military orders. He insisted Rolf travel on a “dumb man”, his coded reference to a false passport; if at any stage Rolf suspected he was being followed after arriving in Sao Paulo, he was to return to his hotel “to hang around town for a few days”, and then travel back to Germany without coming anywhere near his father.

Mengele asked Rolf to bring with him a Latin-English dictionary, parts for his German electric razor, some tape recordings and copies of two books by the Augustan poet Ovid:Tristia and Epistulae ex Ponto, in which Ovid lamented his eternal exile from Rome, just as Mengele did from Germany.

He also requested a book by his friend “Uli”, Colonel Hans Ulrich Rudel, Hitler’s most decorated Luftwaffe ace who Mengele had befriended in Argentina in the 1950s and who’d just caused uproar in the Bundestag having autographed copies of his book at a Luftwaffe air base.

“Naturally, the whole mob of characterless subservients which nowadays tyrannises Germany tear into him,” fumed Mengele, referring wistfully to the fact that even Israel could now teach Germany a lesson in national pride and military strength. Sadly, replied Sedlmeier, most German bookshops no longer carried “Uli’s” wartime exploits.

Finally, on 10 October, Rolf boarded a charter flight to Brazil armed with his own passport, a false passport which he had stolen from a friend to whom he bore a likeness, and $5,000 in cash for his father from the Mengele family.

Sedlmeier meanwhile sent Mengele a word of warning about how Rolf represented a generation of German youth whose ideology and values were wholly different from his own: “The world, especially here with us, has changed tremendously,” wrote Sedlmeier. “And these changes have passed you by… the preconditions that you take as a basis for all actions and thoughts simply no longer exist. The concepts of the old days, which unfortunately — yes, I use the word ‘unfortunately’ — are no longer valid.”

After spending the night in Rio de Janeiro, Rolf boarded a commuter plane to Sao Paulo, and then took three different taxis before arriving at the house of an Austrian couple, Wolfram and Lisolette Bossert, who had sheltered Mengele for years and were now Brazilian citizens. The final leg of the journey was accomplished in the Bosserts’ old Volkswagen, ending at 5555 Alvarenga Rd, a dusty, potholed street. Rolf said the property resembled “more of a hut” than a house.

The man standing at the gate with tears in his eyes to greet Rolf was a shadow of the “Uncle Fritz” he had met 21 years earlier. “The man who stood before me,” said Rolf “was a broken man, scared creature”. Although they embraced, Rolf felt he was in the presence of a stranger.

Mengele graciously gave Rolf his bed, whilst he slept on the floor. When the questioning began, Rolf adopted a conciliatory but lawyerly approach, getting his father to state his case, drawing out his evidence in chief to inform his cross examination to come. “I told my father I was interested in hearing about his time in Auschwitz. What was Auschwitz, according to his version of events? Did he have a role in the things he was charged with?”

According to Rolf, his father strayed into philosophical and pseudo-scientific verbiage, evading the essential points and justifying his racist views, which included a detailed critique of pre-historic evolution.

Then came Rolf’s cross examination. If his father felt so certain of his ground, why had he not turned himself in? “There are no judges, only avengers,” replied his father.

How could he explain that many crippled and deformed people had brilliant minds? “My father couldn’t give a proper answer to that. He just waffled on and on.”

What precisely was his evidence that some races were superior to others? “Here most of his arguments were sociological, historical and political” said Rolf. “They were quite unscientific.”

Wasn’t such an attempt to categorise races immoral and deeply inhuman? “He knew this was my route into Auschwitz and what he did there. He knew I hadn’t accepted what he’d been saying.”

In the 14 days that Rolf spent with his father, he learned a lot about him — the fact that he spoke Latin and Greek, that he was mentally alert — and also about his dark side — his mood swings, his talk of suicide, his depression and his temper. But he learned nothing at all about what his father actually did at Auschwitz, beyond his claim that he “had to do his duty, to carry out orders” and that he had “not invent(ed) Auschwitz”.

Mengele explained to his son that the “Selektions” were analogous to a wartime field hospital where doctors had to make near instantaneous decision on who to save and who to let die. “People were arriving infected with disease, half dead,” his father said, claiming to have done his best to save people by selecting “as many able to work as possible”.

Mengele even claimed that “twins in the camp owed their lives to him” and that he “personally had never harmed anyone in his life”.

Sensing his son’s incredulity, Mengele became angry. “Don’t tell me that you, my only son, believe what they write about me?” he shouted. “On my mother’s life, I have never hurt anyone.”

Rolf said: “These allegations, these facts, left me speechless. I tried to tell him that his presence in Auschwitz alone was unacceptable to me. I was hoping he’d say ‘I tried to get a transfer to the front. I did this; I did that.’” But he didn’t. “Unfortunately, I realised that he would never express any remorse or feeling of guilt in my presence.”

Eventually father and son agreed no useful purpose would be served by continuing the discussion. “There was no point in going on,” explained Rolf. “I had to resign myself to that fact. He did promise to write everything down. He kept saying that if I had time to study what he meant, I might see his point.” But Mengele never did, saying he couldn’t take the risk in case the document one day fell into the hands of the authorities.

Their farewell at Sao Paulo airport was a brief and formal affair, Mengele too preoccupied with his fear that someone might be watching. “We shall try to meet again very soon, all of us,” were his last words. But Rolf knew he would never see his father again. While he had resolved not to turn him in, he had no desire to develop a relationship. A month later, Mengele wrote to his son, thanking him for coming out to see him after so many years’ absence. “Now I can die in peace,” he wrote.

Fast forward 15 months to early February 1979, Sao Paulo’s hottest month. To cool off, Mengele went with his friends, the Bosserts, to a beach at Bertioga. He was in a foul mood, complaining about the heat and his l ife in general. In the late afternoon, he took a dip in the gentle Atlantic waves. Ten minutes later he was fighting for his life. A stroke had paralysed one side of his body. By the time rescuers pulled him ashore he was dead. And there his body lay until darkness fell when the police arrived to take it to the morgue.

Rolf’s first reaction to news of his father’s death was relief. “I basically had a conflict that could never be resolved,” he said. “On the one hand, he was my father; on the other hand, there were these allegations, these horrific pictures of Auschwitz. I was very relived that this solution came about and not another — like maybe a trial, as important as it might have been.”

News of Mengele’s death was kept secret by the family and he was quietly buried under a false name, Wolfgang Gerhard, on a hillside at Embu some 30 miles outside Sao Paulo.

However, in 1985, during a raid on Hans Sedlmeier’s house, the German Federal Police found a letter from Wolfram Bossert. The Brazilian Police were informed and the Bosserts were arrested. Under interrogation, they divulged the location of the grave and the body was exhumed.

On 21 June, Mengele’s bones and his skull were paraded before an eager audience on the 20th floor of the Sao Paulo Police HQ. All the measurements matched those in the meticulous records kept by the SS: his height (174cm), a tell-tale gap between his two upper front teeth, and his broken left finger. “Is there any doubt at all that this is Josef Mengele?” asked a reporter from America’s ABC News. “Absolutely none” replied the forensic odontologist from New York.

As the New York Times commented, Mengele had come to “symbolise the entire Nazi killing project.” And, yes, he eluded justice. Yet, he did serve a sentence of sorts, biding his time in a succession of seedy hideouts, a nasty, embittered, lonely old man, consumed by self-pity and a growing list of painful ailments — knowing his name will forever personify evil.

John Ware is an investigative journalist. Part 1 can be read here.