Immediately after his 10,000m triumph, Mo Farah was asked by the BBC's trackside reporter what it takes to win gold. "It's the grafting and hard work," he said, "120 miles, week in, week out – long distance is a lonely event."

Consciously or not, Farah was echoing a phrase that first drifted into the mind of writer Alan Sillitoe one chilly November morning in 1959. Before his death in 2010, Sillitoe recalled: "I was staring out of the window when this figure wearing shorts and vest came jogging past. I wrote at the top of the page: The Loneliness of the Long Distance Runner. I didn't know what it meant. I thought I might write a poem."

What came out wasn't a poem but a piece of short fiction unlike any other: a torrent of uncensored prose expressing the thoughts of Colin Smith, a 17-year-old borstal boy with a talent for running. "If I had the whip hand," Colin says, "I'd take all the cops, governors, pen-pushers, army officers, Members of Parliament, stick them up against a wall and let them have it, like they'd have done with blokes like us."

For many, the image of Sillitoe's runner is indelibly associated with Tom Courtenay, pounding through the bleak yet beautifully framed landscapes of Tony Richardson's classic film. One of the landmark achievements of the British New Wave, the film is 50 this year. But Sillitoe's proletarian parable shows no signs of ageing: playwright Roy Williams has now created a stage version, updating the action to the aftermath of last year's Tottenham riots in London.

In Sillitoe's book, Colin is sent down for robbing a bakery. Williams's adaptation, presented by Pilot Theatre, finds him convicted for looting a Greggs. This is not Williams' first foray into sport and social disturbances: his 2010 drama Sucker Punch set the rivalry between two north London boxers against the background of the 1985 riots on the Broadwater Farm estate. "I was actually quite wary of focusing on the riots, or even young people again," Williams says. "But then when everything erupted, I felt I had to respond."

Sillitoe's story seemed the perfect vehicle: the famously ambiguous conclusion (in which Colin deliberately loses the race) leaves it up to the reader to decide whether this is an act of rebellion against the established order, or a capitulation. "It was precisely how I felt when I saw the TV images of young people going out on a looting spree," Williams says. "I've almost exclusively made that generation the subject of my plays, and seeing them behave like that brought tears to my eyes. I mean, I love them, and I want to fight for them, but I also feel the urge to slap them sometimes."

Williams has not made any major revisions to the story, but adapted some of the dialogue and brought the references up to date. He has, however, made one significant alteration. In Sillitoe's story, Colin is white; in Williams's version, he is black. Does he think this will influence the audience's perception of the character? "I don't think it alters it at all," Williams counters. "It just seemed right. That's partly down to my own inclination to see young, strong, black characters on stage. But it is a play about a race, rather than a 'race play'."

The alterations were made with the consent of Sillitoe's widow, Ruth, who oversees the writer's estate. Tom Courtenay also accepts that certain aspects of the story may be due for revision. "A friend pointed out recently that a young offender's institution would certainly not be exclusively Anglo-Saxon, and maybe not quite so much like a public school," he says.

Courtenay came from a working-class background in Hull and was freshly out of drama school when Richardson cast him. "Tom was perfect," Sillitoe said. "I actually felt Tom was closer to my image of Colin than Albert Finney had been as Arthur in Saturday Night and Sunday Morning. He had that lean, hungry, aware look." Yet despite having given the definitive performance, Courtenay claims not to have had much in common with the character. "I couldn't empathise with him much at all. His working-class upbringing I could identify with – but I didn't share his rebelliousness or his hatred of society. It was the romantic side of his character that appealed to me – the way he uses his talent as a means of escape. I really wasn't an angry young man at all."

The film was shot entirely on location, in quasi-documentary style, with a minimum of takes. Richardson used borstal inmates as extras, but could not gain permission to film in a real remand home: Ruxley Towers, a Victorian mock-castle in Surrey, had to substitute. "I still see the tower all the time, driving past," Courtenay says. "It gives me the shivers."

Richardson's portrayal of a young offenders' institution now seems mild in comparison with films such as Alan Clarke's Scum; at the time, it revealed a shocking level of brutality and privation that came as a shock to contemporary cinema audiences. The film's sustained attack on the political establishment upset the censors: one report described the film as "blatant and very trying communist propaganda". But it also remains remarkable for its technical innovation: Richardson's use of hand-held cameras and improvisation was ahead of its time – though Courtenay points out that the low budget left its mark. "If you look at the scenes in which I'm running, sometimes I'm wearing socks and at other times I'm not," he says. "That was because they put in some of the earlier test footage, which they didn't have to pay me for."

Courtenay's haphazard running style – all fierce facial contortions and flailing arms – might best be described as untutored. "Time magazine wrote that I had studied [runner Emil] Zátopek," Courtenay laughs. "But I wasn't an athlete at all. I never had to run for more than 70 yards in front of the camera."

Elliot Barnes-Worrell, who plays Colin in the stage version, will not have it so easy. While the film required Sillitoe to pad out his original story with additional scenes and characters, Williams' script unfolds in real time, over the course of the race. The set features an 8m treadmill (the only one of its kind in the country), on which Barnes-Worrell will be required to run for approximately half the show. "That's averaging out as the equivalent of 5km per night," he says, "so I get a genuine sweat on."

Fortunately, Barnes-Worrell, who is making his professional debut, happens to be a member of the alternative London running club, Run Dem Crew. "It started as a group who were looking for the camaraderie of a running club without all the cliques and Lycra," he says. Throughout his time at drama school, Barnes-Worrell ran 10km, four times a week. "But I had to leave the crew in order to prepare for this part," he says. "Running solo is very different. Then it's just you, your heartbeat, your thoughts."