There is a scene at the start of Paddy Considine’s compelling new film, Journeyman, about a boxer who suffers brain damage after a world title fight, that rattles the senses like a sharp one-two.

One moment Considine’s character, Matty Burton, is celebrating retaining the belt with his wife; the next he is dabbing at his head before crashing to the floor unconscious. And, at a stroke, his life’s roulette wheel has spun from glory to tragedy, with no sense it will find equilibrium again.

The movie, which is out on Friday, took Considine nearly 10 years to develop and shoot. But it has timed its moment exquisitely. Boxing in Britain is enjoying another of its sporadic golden ages, despite three deaths in the ring in the last five years, and growing research about the dangers of traumatic brain injury across many contact sports.

Considine’s depiction of a slurring, stumbling former fighter prone to flashes of violence as he tries to rediscover his identity, lingers in the mind. As he explained to me, he wanted to capture not only the bravery of those who put their bodies on the line but “the fragility of the sport and of life itself – and what happens when the doors close and the crowds have gone away”.

From personal experience, I can vouch that he has succeeded. It was boxing that gave my grandfather, Jimmy, the eldest of 15 children scrapping and scraping by in a two-up, two-down in Dublin, a shot at a better life. It led to titles – he was the first Irishman to become European amateur champion – and lasting friendships, including among those who had once tried to take his head off. In truth, he probably prized such camaraderies most of all.

Along the way he also fought in front of 70,000 people at Soldier Field in Chicago, after which the former world heavyweight champion Gene Tunney offered to manage him (he turned Tunney down because he had given the Englishman Ted Broadribb his word he would sign with him). And he also got to face some of the best fighters of his day, including Randolph Turpin, who went on to beat Sugar Ray Robinson.

But, long after he had retired, the sport he loved also killed him. Even with 30 years’ distance, it is hard to forget the panic in my father’s eyes. Or the shock and silence after hearing my grandfather had suffered a heart attack when a heavyweight missed the pads he was holding up at the local amateur boxing club and hit him instead.

What followed sounds like cliché. The local newspaper with its front-page headline “Boxing hero dies in the ring”. The obligatory quote from a family member: “Boxing was his life – he would have chosen to go like this. No blame is being attached to anyone and we feel very sorry for the lad who was training with him.” And everyone moving on, except those involved.

It is on this difficult terrain that Journeyman pokes and probes. Considine, who prepared for the role by training for 12 weeks at the Ingle Gym in Sheffield (my great-uncle Brendan also has a cameo as his father), admitted to me that he was nervous that his film might be seen as anti-boxing. He needn’t be. Only someone who cared about the sport would depict it so honestly. Journeyman does not glorify boxing or condemn it. It merely recognises its dangers.

No one can accuse Considine of not doing his due diligence. Before making the film he spoke to Peter McCabe, chief executive of the brain injury charity Headway, who is deeply anti-boxing, as well as surgeons and those with brain injuries.

“Sometimes we look at boxing and we forget there are human beings in there – they become characters in a narrative themselves,” he said. “And with that separation you sometimes forget there are two men putting their lives at risk.”

I thought of those words on Saturday night as the Australian heavyweight Lucas Browne crashed face-first on the canvas during the sixth round of his fight against Dillian Whyte. It had long been obvious that Browne – a strong but primitive fighter reminiscent of an early character in a Super Punch Out! – was in trouble. He was bloodied and blinded, nose busted and physically gassed. Yet he was allowed to continue by his corner and the referee until a cuffing left hook knocked him out for several minutes.

Afterwards some people on social media suggested that Browne still had a puncher’s chance. Perhaps he did. But at some point in the fourth or fifth round, when the chances of him landing that sort of shot became smaller than the risk of being seriously hurt, the fight should have been stopped.

Sometimes I wonder whether social media is partly to blame. No one wants to be labelled a coward or a quitter. And so they continue to trudge into the firing line.

Thankfully on Sunday Browne tweeted that he was fine, but tellingly he also admitted: “My eye was giving me trouble from the second and you can’t protect from what you can’t see.”

I still maintain that boxing redeems far more lives than it ruins. And I have also seen the power of the salve and salvation that boxing clubs can provide in inner‑city communities at first hand. But it is always good to have your prejudices challenged. Journeyman certainly does that.