When Bert Trautmann arrived at Manchester City in 1949, 20,000 protested against his signing. By the time he left, he was lauded as the bravest man in British sport

Bert Trautmann begins looking a little bored when the broken neck is mentioned. After spending almost an hour discussing Nazism, the horror of war, antisemitism and failed relationships with impressive and sometimes chilling candour, the former Manchester City goalkeeper's still bright-blue eyes finally start glazing over.

"I've explained it 1,636 times on this trip already," he says, smiling thinly, as the conversation shifts to the 1956 FA Cup final and the day he played the last 16 minutes of City's triumph over Birmingham with a fractured neck. "Wherever I go, people always ask about my neck."

It had been no surprise when the 86-year-old German's visit to Eastlands last week, to promote Catrine Clay's brilliant new biography Trautmann's Journey, began with City's club doctor bounding towards him clutching an anatomical model of a human's upper body.

"I still have pain if I make unexpected movements of my head," says the one-time Luftwaffe paratrooper and holder of the Iron Cross, who will be rooting for City from the Eastlands directors' box during this afternoon's latest rematch with Birmingham. "But I was very lucky: surgeons told me I could have died or been paralysed."

Instead, Trautmann, in infinitely better shape than most men a decade younger, was able to continue living what he acknowledges is an "extraordinary, sometimes mad" life to the full.

Many of its happiest moments arrived in later years when, employed by the German government on a third-world initiative, he lived in Burma, Tanzania, Liberia, Pakistan and Yemen. "Excellent times," he says. "I was teaching people how to be football coaches, but they all taught me a hell of a lot about life, about tolerance and thinking differently."

By then Trautmann had already completed an incredible odyssey that swept this one-time Hitler Youth prodigy into active wartime service in Russia and later France. "I volunteered when I was 17," he says. "People say 'why?', but when you are a young boy war seems like an adventure. Then, when you're involved in fighting it's very different, you see all the horrible things that happen, the death, the bodies, the scariness. You can't control yourself. Your whole body is shaking and you're making a mess in your pants."

Trautmann was one of only 90 members of his original 1,000-strong regiment still alive in 1945. Several fellow survivors were left badly maimed. "I kept nothing from the war," he says. "I don't have my Iron Cross any more."

Earlier, he had endured a childhood of brainwashing, experiencing years of indoctrination during racial biology and ideology lessons in which messages that Jews were responsible for wrecking Germany's economy, that Poles were an inferior people and Aryans the master race had been repeatedly rammed home.

"Growing up in Hitler's Germany, you had no mind of your own," he says. "You didn't think of the enemy as people at first. Then, when you began taking prisoners, you heard them cry for their mother and father. You said 'Oh'. When you met the enemy, he became a real person. The longer the war went on, you started having doubts. But Hitler's was a dictatorial regime and you couldn't say what you wanted. In the German army, you got your orders and you followed them. If you didn't, you were shot."

After he escaped from the Russians and then the French resistance, the British finally captured him properly. "When they got me [after he had hurdled a fence leaping straight into an ambush] the first thing they said was: 'Hello Fritz, fancy a cup of tea,'" recalls Trautmann.

It was the start of an unlikely love affair. "I feel British in my heart now," he says. "When people ask me about life, I say my education began when I got to England. I learnt about humanity, tolerance and forgiveness." Not to mention that Jews were human, too.

Trautmann was told of concentration camps and the Holocaust in an English PoW camp, but his first intimation that something had gone very wrong came when, fighting in Ukraine, he and a friend inadvertently stumbled across a massacre of Jews by SS officers in a forest. After being herded into trenches, they were systematically shot. Terrified, the pair escaped undetected and never spoke of the incident. Trautmann bows his head at the memory: "I was 18."

German PoWs were routinely shown a film about Belsen. "My first thought was: 'How can my countrymen do things like that?'" he says. "But Hitler's was an utter totalitarian regime."

Later, the then 22-year-old worked as a driver for Jewish officers on the camp. "They wanted to know what you thought about Nazis and the Jewish community," says Trautmann, who admits that "deep down" he then still viewed Jews as moneylenders and profiteers.

"Sometimes their questioning was quite nasty, your pride was hurt and I lost my temper." So much so that after one called him a "German pig" Trautmann punched him.

Subsequent driving service for another Jew, Sergeant Hermann Bloch, proved much happier. "I quickly came to see Bloch, and every other Jew, as human beings. At first I sometimes lost my temper with him, but, in time, I talked to him as if he was just another English soldier. I liked him."

He also enjoyed playing centre-half for PoW teams across north-west England, only being persuaded to move into goal after one day becoming embroiled in an outfield fight. A star was born and, with Trautmann declining repatriation to Germany, a stint at non-League St Helens prefaced a high-profile move to Manchester City.

Manchester boasted a sizeable Jewish community and 20,000 demonstrated against City's new signing before Dr Altmann, the communal Rabbi, appealed for the German player to be offered a chance, reminding everyone that an individual should not be punished for his country's sins.

"Thanks to Altmann, after a month it was all forgotten," says Trautmann. "Later, I went into the Jewish community and tried to explain things. I tried to give them an understanding of the situation for people in Germany in the 1930s and their bad circumstances. I asked if they had been in the same position, under a dictatorship, how they would have reacted? By talking like that, people began to understand."

Trautmann's personal world turned dark and unfathomable a month after the 1956 FA Cup final, when his six-year-old son John was run over and killed. Although his then wife Margaret bore him two more boys, she never recovered. "Margaret didn't get over John, she had no interest in life any more," says Trautmann, who, after an unhappy stint managing Stockport – where he was horrified to discover Coronation Street actors influenced the chairman – would eventually walk out on her and into that German government job. "When she died, it was of a broken heart."

Tall, blond and devastatingly handsome, Trautmann caused his fair share of emotional grief. After getting his first girlfriend, Marion, pregnant, he abandoned her and baby Freda shortly after the birth. "Marion didn't have an easy life. I left her with a PoW's bastard daughter and, although I gave her maintenance, it was very little. The most I ever earned at City was £35 a week," Trautmann admits. "But I was terrified of being trapped."

A decade ago, Freda traced him, they are now close and he has been re-introduced to Marion: "She told me, 'You did the right thing, I can't blame you'. Imagine having such generosity."

Always close to his mother, Trautmann is haunted by the repercussions of that post-war refusal to return to Bremen. "Mutti's relationship with my father wasn't so good and my decision to stay in the UK was another hardship," he says. "I think she died of a broken heart."

Such brutal honesty and acute self-awareness is rare, but he is an unusual man. If his private life – Trautmann is happily married to his third wife, Marlis, and living in a modest bungalow on the Spanish coast near Valencia – has not always been exemplary, he remains a peerless ambassador for international reconciliation.

"Travelling is the best education," says the holder of an OBE, awarded in recognition of unstinting work improving Anglo-German relations. "It teaches tolerance and understanding."

The importance of these cannot be underestimated. "We never, ever, want another world war," stresses the old Luftwaffe paratrooper. "It absolutely must not happen."