It is little over a month since Kimani Gray, a 15-year-old black youngster, was shot and killed by police in highly-contentious circumstances in the Flatbush area of Brooklyn, not all that far from the location of the vanished and mourned 1950s baseball shrine of Ebbets Field, home to the – also vanished – Brooklyn Dodgers.

When the Dodgers fled to Los Angeles at the whim of owner Walter O’Malley – for decades a loathed name in the borough – the stadium was bulldozed and replaced by the Ebbets Field apartments, which were in turn renamed the Jackie Robinson apartments in honour of the Dodgers’ – and major league baseball’s – first black player. That mid-century era of Coca-Cola in real bottles, of gleaming cars with artwork designs and casually-obscene racism is brought to life in the film which has drawn spectacular box office receipts across America this week.

42 is both the number Robinson wore and name of the first major Hollywood treatment of his life. It was no coincidence the film's opening was on the week of the anniversary of Robinson's debut for the Dodgers and as a salute, every single player on every major league baseball team in America wore number 42 for the scheduled games on Monday last.

Robinson’s debut in 1947 ended what had been a code of observation rather than an official rule in major league baseball: the so-called Negro Leagues were deemed sufficient for the black population of America and no front-office manager had even considered signing a non-white player until Branch Rickey – wonderfully portrayed by a crusty and unimpeachable Harrison Ford in the film – had both the commercial canniness and moral courage to realise that the times were a changin’.

Like most sporting films with a biographical nature, 42 is predictably honest and full-hearted and earnest and uses typical scenes – the tobacco-chewing general manager of the Phillies with the best Southern drawl since James Dickey's turn as sheriff Bullard in Deliverance , the entire Brooklyn team turned away from a hotel because Robinson was in their party, the common use of the word "nigger" (it causes a stir in Lincoln , set in the 1860s: it is more shocking when set against Buddy Holly era of America) and the simmering hostility directed at Robinson by several of his team-mates.

It helped that Robinson had both a devilish and cussed streak as an athlete. His signature move was to drift dangerously far from his base, distracting the pitcher as he stood crouched with both arms moving in a constant, jittering shake, relying on his speed to beat the thrown ball back to the base point.

Star attraction
Robinson had poise and obstinacy and his arrival prompted floods of African-Americans through the turnstiles at Ebbets Field while paving the way for baseball players from other ethnic groups to sign major league contracts. He was the equivalent of Rosa Parks in a sporting context (and Parks's refusal to give up her bus seat to a white passenger occurred in 1955, some eight years after Robinson's admittance to baseball) and in the decades since he broke the taboo he has gone from being baseball's most unwelcome arrival to perhaps its most honoured player.

But the great unanswered question in the film is for how much longer baseball’s apartheid system would have prevailed if Branch Rickey had not been so cussed. The resistance to Robinson’s arrival was sufficiently staunch – threatened boycotts, hate letters, vitriol in the stands and several attempts by opposing players to injure him – to suggest ruling America would have been happy to keep major league baseball white long after 1947.

In 42 , the transformation of white America is represented by the slow drift of applause through the white sections of the stand, the gradual recognition among Robinson's team-mates that his audacity and skill makes them pennant contenders, and the lone comedic scene when a Dodgers player invites Robinson to take a shower with him as the player had always waited until his team-mates had finished. "Not in that way," he says to Robinson's amusement.

But, of course, the transformation was nothing like as clean cut or as swift. The reason director Brian Helgeland plays with such a straight bat is he is tackling the most slippery and volatile subject in America: race. Just because black music and sports stars are feted now doesn’t mean skin colour has ceased to be an issue. Ask anyone who grew up in the vicinity of Kimani Gray. Or ask the Miami Heat basketball team why they posed in hoodies in sympathy with Trayvon Martin – another black teenager shot dead for being in the wrong place at the wrong time – and most could probably explain they had been in that situation themselves.

Or ask why the “good” parts of New York can exist with the social housing projects and it is as if some invisible wall keeps both places apart. Or ask any young man whether it is easier to be white and 20 or black/hispanic and 20 and they will all agree that for non-whites, it is just different. Or ask the question that has been raised in the wake of the latest atrocity: how did it happen that the first suspect in the Boston marathon attack was just another at the scene and a Boston resident, wounded by the blasts and indistinguishable from thousands of others except for the fact his skin colour was different and it was quickly established that he was of Saudi Arabian ethnicity?

The days when people could casually lob racial smears over the fence as they did at Robinson have long disappeared and the word “nigger” is probably the single most taboo word in American English. It has become off limits for whites. In fact, the opposite pertains now. The prevailing code of communication between people of all ethnicities is of fastidious politeness.

Race is rarely mentioned but it is always there and the huge reaction to 42 is an uncomfortable reminder of the fact segregation and official racism was alive and well in the US less than a lifetime ago.

Not far from the theatre where the film showed, three men in suits strode down the street and one loudly (volume of choice in New York) told his companions: “Man, I was just at the most racist table you could ever meet.”