The Loneliness of the Long Distance Runner

The film opens with Colin Smith (Tom Courtenay) running, alone, along a bleak country road somewhere in rural England. In a brief voiceover, Colin tells us that running is the way his family has always coped with the world's troubles, but that in the end, the runner is always alone and cut off from spectators, left to deal with life on his own.
Colin is then shown with a group of other young men, all handcuffed. They are being taken to Ruxton Towers, a detention centre for juvenile offenders, an approved school. It is overseen by "the Governor", who believes that the hard work and discipline imposed on his charges will ultimately make them useful members of society. Colin, sullen and rebellious, immediately catches his eye as a test of his beliefs.
An important part of the Governor's rehabilitation programme is athletics, and he soon notices that Colin is a talented runner, easily able to outrun Ruxton's reigning long-distance runner. As the Governor was once a runner himself, he is especially keen on Colin's abilities because, for the first time, his charges have been invited to compete in a five-mile cross country run against Ranley, a nearby public school with privileged pupils from upper-class families. The Governor sees the invitation as an important way to demonstrate the success of his rehabilitation programme.
The Governor takes Colin under his wing, offering him outdoor gardening work and eventually the freedom of practice runs outside Ruxton's barbed wire fences. A series of flashbacks shows how Colin came to be incarcerated: his difficult, poverty-stricken family life in a lower class workers' complex in industrial Nottingham. Without a job, Colin indulges in petty crime in the company of his best friend, Mike (James Bolam). Meanwhile, at home, his father's long years of toil in a local factory have resulted in a terminal illness for which he refuses treatment. Colin is angered by the callousness of his mother (Avis Bunnage), who he knows already has a "fancy man", and who Colin finds has neglected to give his father a herbal concoction for pain and (as Colin believes) brings about his father's death.
Colin rebels by refusing a job offered to him at his father's factory. His father's company has paid Â£500 in insurance money, and he watches with disdain as his mother spends it on clothes, a television and new furniture. When his mother moves her lover into the house and after an argument when she tells him to leave, Colin and Mike take to the streets. Colin uses his portion of the insurance money to treat Mike and two girls they meet to an outing in Skegness, where Colin falls in love with his date, Audrey (Topsy Jane), and confesses to her that she is the first woman he's ever had sex with. She eventually extracts a half-hearted promise from Colin that he might look for work, implying his feelings for her are such that they might marry.
But one night, while prowling the streets of Nottingham with Mike, the two spot an open window at the back of a bakery. There is nothing worth stealing except the cashbox, which contains about Â£70. Mike is all for another outing to Skegness with the girls, but Colin is more cautious and hides the money in a drainpipe outside his "prefab". Soon the police call, accusing Colin of the robbery. He tells the surly detective (Dervis Ward) he knows nothing about it. The detective produces a search warrant on a subsequent visit, but finds nothing. Finally, frustrated and angry, he returns to say he'll be watching Colin. As the two stand at Colin's front door in the rain, the torrent of water pouring down the drainpipe dislodges the money, which washes out around Colin's feet.
This backstory is interspersed in flashbacks with Colin's present-time experiences at Ruxton Towers, where he must contend with the jealousy of his fellow inmates over the favouritism shown to him by the Governor, especially when the Governor decides not to discipline Colin, as he does the others, over a dining hall riot over Ruxton's poor food. Colin also witnesses the kind of treatment given to his fellows who are not so fortunate â beatings, bread-and-water diets, demeaning work in the machine shop or the kitchen.
Finally, the day of the five mile race against Ranley arrives, and Colin quickly identifies Ranley's star runner (played by James Fox). The proud Governor looks on as the starting gun is fired. Colin soon overtakes Ranley's star runner and has a comfortable lead with a sure win; but a series of jarring images run through his mind, jumpcut flashes of his life at home and his mother's neglect, his father's dead body, stern lectures from detectives, police, the Governor, the hopelessness of any future life with Audrey. Just yards from the finish line, he stops running and remains in place, despite the calls, howls and protests from the Ruxton Towers crowd, especially the Governor. In close-up, Colin looks directly at him with a rebellious sneer, an expression that remains as the Ranley runner passes to cross the finish line to victory. The Governor is intensely angry.
At the end, Colin is back in the machine shop, punished and ignored by the Governor. But he seems calm â even content â with his loneliness, because he has refused to submit to authority.

Question: What shows how Colin came to be incarcerated?
Answer: a series of flashbacks