When I began working at the Freie Universität Berlin last September, I put up on the door of my office a photo of Bernhard Trautmann, captioned with Lev Yashin’s remark: ‘There have only been two world-class goalkeepers. One was Lev Yashin, the other was the German boy who played in Manchester, Trautmann.’

Trautmann is the subject of The Keeper, a movie that opens in Britain today and has been playing in Germany since the middle of March. Born in Bremen in 1923, he joined the Luftwaffe at 17. As a paratrooper he fought on both the Eastern and the Western Front and won medals including the Iron Cross, before being captured by the British and sent to a POW camp in Lancashire. He stayed in Britain after his release, living and working in St Helens and playing in goal for St Helens FC.

‘Bert’ signed for Manchester City in October 1949. Famously – I learned this about Trautmann as a child before I had ever seen City play – he broke his neck in the 1956 FA Cup Final but played on to see City to victory. Perhaps he had taken to heart the pre-match words of the captain, Roy Paul (who had been a physical training instructor in the Royal Marines during the war): ‘If we don't fucking win,’ Paul is supposed to have shouted, waving his fist, ‘you'll get some of this.’

According to legend, Trautmann’s arrival at City was immensely controversial, sparking threats of a boycott and a street demonstration of 20,000 people. ‘If they sign this German goalkeeper,’ an anonymous ‘Jewish City Supporter’ wrote to the Manchester Evening News, ‘I will organise a boycott among the thousands of men belonging to the Jewish ex-servicemen’s club who are City supporters, and also among British Legion members of the Cheetham branch.’

His performances on the pitch, along with the intervention of Rabbi Alexander Altmann, are said to have reconciled Manchester to Trautmann. ‘Despite the terrible cruelties we suffered at the hands of the Germans,’ Altmann wrote, ‘we would not try to punish an individual German who is unconnected with these crimes of hatred. If this footballer is a decent fellow, I would say there is no harm in it.’ Altmann’s gesture plays a central role in The Keeper, though as Sven Goldmann pointed out in Der Tagesspiegel, the film depicts Altmann as responding at the urging of Trautmann’s English wife – a retelling of the story that robs him of the capacity to forgive the German on his own terms and in a manner of his own choosing.

There is no evidence that the fabled demonstration against Trautmann ever took place. ‘It doesn’t matter two hoots,’ one fan wrote to the Evening News soon after he was signed, ‘if City’s goalkeeper is German or English, black or white, Catholic or Protestant, Jewish or Gentile. It would only matter if he were a Fascist – or a poor goalie!’

Match reports in the Manchester Guardian made no reference to the controversy, noting only that City were ‘fortunate, so soon after Swift’s retirement, to find a personality like Trautmann to guard their goal’. ‘Even allowing for the comparative lack of interest shown by the national sports press of the time in events off the field of play,’ Stephen Wagg argues in On and Off the Field (2013), ‘this does not read like the description of a man at the eye of a political storm.’ The Jewish Chronicle noted ‘controversy in Manchester’, but indicated that a boycott was unlikely to take off.

Sports movies like outsiders, and narrative arcs that ascend, if not towards victory, then at least towards some achievement that redeems the protagonist. In The Keeper, as the director, Marcus Rosenmüller, has pointed out, the achievement is Anglo-German reconciliation. ‘It has become a very current movie’ in this time of ‘populists and Brexit’, he told an interviewer from the liberal Süddeutsche Zeitung.

Filmmakers are entitled to smooth off the rough edges of a story. And I enjoyed the film well enough when I saw it a few weeks ago at the Zoo Palast, a cinema opposite the Kaiser Wilhelm Gedächtniskirche, a Lutheran church damaged by an air raid in 1943 and left as a memorial. But by exaggerating what was required in Manchester in 1949 (in order to celebrate what Wagg calls ‘a purportedly special British capacity for tolerance’), it misses the extent to which ‘Bert’ had already settled – however partially or precariously – into the working-class community in St Helens, wearing a cloth cap and muffler and drinking in local pubs. When Trautmann visited Bremen in 1949, his brother told him: ‘You’re a bloody Englishman now.’