A Tuesday in mid-January. Grey skies, five degrees, one o’clock. A man stands outside his ­high-street flat in Richmond, west London. He wears a thin black jacket, black shorts, black socks and red size 11 trainers. With his winter fat he weighs nearly 15 stone.

The man starts to run, his footfall light and his breathing heavy. I always sound like this to start with, he says – after two miles you won’t hear me. After two miles he is silent. He has not planned a route or a distance, which is how he likes it. In Hammersmith the pavement is crowded and the man weaves between the pedestrians. No one gives him a second look. And why should they? I am an OK runner, he says.

Is this true? If speed is the only measure of athletic excellence, then yes. The man moves at his comfortable pace, eight minutes a mile, only half as fast as Roger Bannister did 62 years ago. But listen to his answer when asked about his endurance levels after nine weeks without exercise. “I could keep running like this for one and a half days,” he says, then corrects himself. “Two days.”

This is true. Less than two years ago the man was a 31-year-old office worker who had never run a marathon. Twelve months later he had completed a greater number of 26.2-milers in 365 days than anyone in history – more than one a day. Four months after that, he did something even more remarkable, and also unprecedented: ­running the equivalent of more than 14 marathons, back to back – a crow’s flight from Tunbridge Wells to Glasgow – without sleeping.

The man crosses one bridge over the Thames and then another the opposite way, looping back towards the high street, past the charity shop where he buys toys for his three-year-old son, to the flat where his pregnant fiancée is making cauliflower soup. He’s not a great runner, he insists. His gift is mental strength and an extraordinary ability to endure pain. He learned to do that a long time ago.

****

Where does the Rob Young story begin? Maybe it is on Sunday 13 April 2014, the day of the London Marathon. Thirty-six thousand men and women line up at the start. Most have trained for several months; for some, this will be the hardest thing they have ever done.

Young is on his sofa, a bag of crisps on his lap, watching the television coverage. The occasional 3.1-mile parkrun is the limit of his running ambition but he enjoys the spectacle of the marathon, seeing all those people raising money for charity. When Joanna, Young’s fiancée, asks him to go to the park with her and their infant son, Alexander, he protests, saying he plans to run the race some day.

“You can’t run a marathon,” she says.

“I bet you 20p I can,” he replies. “I reckon I could do 50.”

This is crazy, they both know. But that ­afternoon Young has a strange feeling, which, when he later describes it, sounds like an epiphany: “It was just complete relief. In that moment I found I broke through all the barriers holding me back.”

From the internet he prints out the route map of the Richmond Marathon, which goes around the park. That night he lays out a T-shirt, shorts and an old pair of trainers and packs his office clothes in a backpack. When his alarm rings at 2.30am he springs out of bed and cycles to the park. Joanna expects him back in a hour, perhaps two, after completing seven miles at the most. Nobody runs a marathon with zero training. Especially not in the dark, alone, on a course with more than 1,000 feet of climbing.

Young does not come home that morning. Although he has to walk part of the way, he completes the full distance in just over four hours. He changes clothes, rides to the train station and does a day’s work at the small auto parts business he manages in West Hampstead. In the evening, he calls Joanna and says he’ll be home late. He returns to Richmond Park and runs another 26 miles. This time he is 40 minutes faster. Young is shattered, and exhilarated.

The next morning at 2.30am he is up and running again. Twice more that week he does two marathons in a day. After seven days he has completed ten marathons. Maybe 50 is possible. Yet Young is no longer thinking about 50 – or only about himself.

****

Or maybe the story starts before then. It is the late 1980s. A six-year-old boy sits in his bedroom in a small village in Yorkshire. It is evening and soon his father will be home. The boy is terrified. His father is a drunk, prone to bouts of extreme physical and psychological violence. Rob Young knows what is coming, and he knows that he cannot run.

****

On 30 November 2013, a 68-year-old American lawyer named Larry Macon broke his own Guinness World Record when he completed his 239th marathon in a year. Other people had run more 26-milers over 365 days, but not in organised races: in the year to October 2011 the Spaniard Ricardo Abad ran one every day, equalling a record set that February by the Belgian Stefaan Engels. This is the unofficial record Young targets. He builds a website, Marathon Man UK, with a page for donations to children’s charities. To raise awareness of his appeal he decides to do all his runs wearing a kilt. When he tells his friends what he is doing they say two things. The first is: that’s impossible. So he invites them to come to see for themselves, and they do, rising before dawn to head to various points in Richmond Park, waiting for Young to emerge from the gloom, and then running or cycling with him part of the way. Others bring food or drinks for him, which they stash in tree trunks or at the park gates.

The second thing people say is: Rob, you are going to harm yourself. When Ricardo Abad set his record he was also working full-time, in a factory. He told the Spanish sports newspaper Marca that the key to his success was sleeping eight hours a night and eating healthily. Young is sleeping three to four hours, running on an empty stomach and then consuming whatever food he can find – burgers and milkshakes are his favourites – to replace the more than 3,000 calories he burns during each marathon. Ali Parkes, a friend who agrees to help him fundraise for the charities, ropes in a team of medical experts to offer counsel – a sports doctor, a physiotherapist, and a dietician who draws up a ten-page eating plan. Young listens patiently to all the advice and ignores most of it.

He prefers to figure things out for himself. The usual long-distance strategies – keeping a consistent pace, or accelerating slightly towards to the end – do not work when you are running one or two marathons a day, he finds. Instead, he divides each run in half. For the first-half 13.1 miles he pushes himself, aiming to finish in about 90 minutes. Then he jogs the rest of the way in two hours or more; this is his recovery for the next run.

He suffers silently: his nipples bleed from the chafing, and he loses a few toenails and nearly three stone. But after a month of running his confidence is high. A few weeks is all you need to get used to a marathon a day, he tells people. This should make Young happy, but he is troubled: his challenge has become too easy.

On weekends he enters official marathons, and he begins to seek out ever more demanding events, involving hills and off-road trails, or ultramarathons, which range from 31 miles to 140 miles. (His rule is that each race, no matter how far, counts as only one marathon for the purposes of the record.)

If no ultra is scheduled, Young creates his own. One evening in July, he catches a train to Watford, alights and jogs 56 miles alone through the night to the start line of a marathon in Northampton, and then on to the finish.

A few weeks later he takes what looks like a casual stroll. Shortly after midnight on a Friday, he runs his usual solo marathon in Richmond Park. A friend then drives him straight to the start of the North Downs Way 100-miler, one of the toughest races in the country, with nearly 10,000 feet of ascent. The goal is to finish in less than 24 hours. Thirty-six out of the 180 starters do, including Young, in a time of 23 hours and 53 minutes. A photo included in the official race report shows him running in his kilt, chin raised, wide smile, arms spread out like a child frolicking in a fountain. At the end he gets a lift to Salisbury and completes a trail marathon. In a day and a half, he has run more than 152 miles on less than two hours’ sleep.

When he does get a bit more rest it is ­seldom comfortable. Because he needs to limit his expenses, and has little time to look into logistics, he regularly sleeps rough before a race. Arriving in Somerset before the Cheddar Gorge Marathon, he calls Pippa Rollitt, the physiotherapist who has been advising him. It is evening and the weather is terrible. He has a tent but thinks the wind will blow it away.

“I’m going to sleep in a cave,” he tells her. “I’ll be OK, it’s close to the start line.”

When people see how hard Young is pushing himself – even in the highly driven, obsessive world of ultrarunning he is a freak, wearing through a pair of running shoes in two weeks or less – they wonder: what is driving him? He does not seem interested in glory and plays down his achievements: it’s a little bit of running, a little of pain. When there are opportunities for self-promotion, he is hard to reach – he dislikes mobile phones, much to the frustration of those trying to help raise ­publicity, and of Joanna, who often has little idea how he is faring on his epic weekend adventures.

Then when people hear the story of his childhood, they think they know why he is running – Rob Young must be trying to escape his past.

****

The boy’s father likes sadistic games. One of his favourites is locking his son in a hard suitcase and pushing it down the stairs, leaving him battered and bruised. Another is dangling him over the ­banister by one foot. If the boy makes a sound, he is dropped. Young learns to control his breathing, exhaling slowly in a sort of silent scream. “I would block everything out: it was like pushing my eyes to the back of my head, putting all the pressure there,” he says.

One day, Young picks up a church leaflet that comes through the letter box and takes it to his bedroom. When his father finds it there he drags his son to the top of the staircase and gets a hammer and a nail. He drives the nail through the boy’s foot, and then into the banister.

Young’s sister is also victimised – sexually abused by her father while the brother is made to watch – and then dragged into the violence as a perpetrator. When Young takes one of her sweets, their father instructs her to stab her brother in the leg with a fork, which she does.

So when the father ties a rope around Young’s neck, and loops it around the metal coat hook behind a door, the boy feels a sense of relief. His father has already killed the family dog in a similar way. Young cannot breathe, he is going to die, it will all be over. His father loosens the rope and lets him down.

****

As the summer goes on Young’s body takes the strain. When his knee balloons he has the fluid drained out of it and runs a marathon the next day. In the office he always looks tired, and although he insists that his work is not suffering, the boss urges him to cut down on his running. Young quits his job instead.

To help him and his family save money, his friend Ali Parkes invites them to move out of their rented flat and into his home. Parkes has three children; his daughter gives up her bedroom. Young often sleeps on the living-room sofa in his running clothes, but is so tired that his alarm goes off six or seven times before he rises. Parkes takes to working until 3am, so he can shake Young from his slumber. “He would put on his shoes with his eyes closed,” Parkes says. “He always said that was the hardest thing: getting out the door.”

By the time Young reaches the park he is fully awake. He never runs with music – he regards it as a stimulant and wants to run on willpower alone – and prefers the dim light of the moon to a head torch. Some mornings, when the mist is thick, he finds himself among a herd of deer, or face to face with a stag. No harm comes, and Young thinks that the animals have got used to him.

With his working hours now free, Young gives talks in schools and community groups. Children listen with rapt attention as he tells them how an ordinary man runs extraordinary distances – and about overcoming the abuse he suffered as a child. Shame is the thing that holds victims back, he says. “What happened to me was not my fault. And if something like that happened to you, it is not your fault either.”

One morning, a woman waits for him at Richmond Park to tell him that her son killed himself after being abused by his father. Please carry on what you are doing, she says – you are getting through to people. Another time, after a talk at a Women’s Institute, a mother approaches him to say that her child, also a victim of paternal violence, had heard Young speak at his school and drawn strength from his story.

Young is deeply moved. His marathon quest was never a way of escaping from his past, as some people assumed – he made his peace with that long ago, and had spoken openly to friends about his terrible childhood for years. For a long time he believed that the reason he survived was so he would be able to help other people, especially children, one day. And now he has found a way to do so: he is running to “inspire people and to bring hope”.

And, of course, trying to test his limits. Towards the end of November 2014, seven months in to his record attempt, he finds them. His left shin and ankle swell so much that he runs with a limp. He is persuaded to call again on Courtney Kipps, a sports doctor and assistant medical director of the London Marathon, who has monitored his progress since a month after he began his challenge. Kipps has been sufficiently astounded by Young’s casual approach and ability to withstand injury to want to study him in his laboratory at the Institute of Sport, Exercise and Health.

“Here’s a guy under great stress, not sleeping or eating well, with financial and family worries – it’s a perfect storm,” Kipps says. “Yet he carries on. Day by day he defies expectations.”

When Kipps looks at Young’s ankle he orders a scan, which shows bruising in the bone. If he carries on running he will surely get a stress fracture, which can become a full fracture if he pushes through the pain. His quest is over.

****

After the hanging scare, Young’s mother, who suffers her own abuse at the hands of her husband, finds the courage to call social services. She and the two children are moved to a safe house, and then travel to Hampshire – walking part of the way and sleeping overnight in a ditch – to be near her parents. But she is unable to look after two children and so, aged eight, Young is put in a care home, where he is bullied, and in turn becomes a bully.

When he is 12, Young meets a deputy headmaster and part-time coach named Peter Wells at a sports club. Wells applies to foster Young, and becomes the father he never had, helping him with his schoolwork and teaching him about manners, respect and life.

On finishing secondary school, Young joins the army, serving in the Royal Corps of Signals. Competitive and headstrong, he spends much of the time in a tracksuit, doing triathlons and biathlons. He is good enough to make the junior GB team. But one discipline always lets him down – the run, which he hates. Aged 23, he leaves the army and briefly rides with the Milram professional cycling team in Italy before returning to the UK to be with his pregnant girlfriend. After a few years, they split up. Young re-establishes contact with his mother and sister, though they never become close. He meets Joanna on a dating site, bringing her a salmon covered in wrapping paper and a bow as a gift the first time they meet. “She said she likes fish!”

They fall in love and he becomes a father for the second time. They lead a quiet, contented life. And then they make the bet.

****

Never give up. That is Young’s motto, and he lives it. Kipps tells him that the injury usually requires a minimum of three to four weeks of complete rest, and then a gradual reintroduction to running. That would rule Young out of the Race Across USA, in which 12 amateur athletes will run the equivalent of 117 marathons over four and a half months, from Los Angeles to Washington, DC.

Twenty-three days after the scan he runs a marathon. Though he can no longer break the record for the number of marathons run on consecutive days over a year, his habit of completing two 26-milers on some days gives him room still to improve the mark for the total number of marathons.

He arrives in Los Angeles keen to make up for lost time, and quickly takes the overall lead in the race. His fellow competitors soon learn what anyone who runs with Young does: the man who never had a proper childhood is a kid at heart. He loves to play the fool (lying down in the road so others have to jump over him), to dance (a fairy jig) and to sing (“I love you baby . . .”). And he does not like to do his homework: while the others study the daily route maps and download directions on to their GPS watches, he prefers to wing it – and repeatedly gets lost.

It is also obvious to all that Young is stressed. He knows he is an absent husband and father who is putting the family’s future in jeopardy. Since leaving his job, he has used up his savings. There is no cash coming in, which worries Joanna, who has moved back to Poland with Alexander to stay with her parents. Though she is greatly supportive of Young’s running, she hates being so far away from him, and being dependent on others. “We were fighting all the time,” Joanna says. “We were on the border of splitting up.”

She asks him to come home, and he agrees. They talk some more and decide he should carry on. “To have quit would have ruined me as a person,” he says.

He does not hide it when he thinks the race organisation is lacking. Bryce Carlson, an American ultrarunner who eventually finishes second, describes Young as the most volatile runner in the group, playful one moment, yelling and pouting the next. “He probably ‘quit’ the race at least five times, always making a bit of a fuss, but he always managed to show up at the starting line again the next morning,” Carlson writes in an email.

He notes that they do not always see eye to eye, but also that he became very fond of Young, who would often slow down in order to chat to the other runners. “Another small thing: he was extremely generous with his food. He would routinely purchase more food than he needed or wanted so that he could share with others. I remember a number of occasions where he would want to stop mid-run for a soda, ice cream, or Popsicle and offer to pay. If you said no thanks, he’d often stop and buy you one anyway.”

On 10 April 2015, in Mississippi, 362 days after his first marathon, Young celebrates breaking Abad’s record. (He has in fact run 367 marathons at this point, believing Abad to have run 366 in a year, not 365). He wins the Race Across USA by 30 hours.

****

Daniel Lieberman is a professor of human evolutionary biology at Harvard University, and an expert on the biomechanics of endurance running. At the start and end of the Race Across USA he performs tests on the competitors. He finds that Young has “the perfect running form”: good posture, a relaxed upper body, a seemingly effortless glide. Many amateur runners crash into the ground with their feet. When Lieberman asks Young to run on a pressure pad, there is very little impact.

“That’s important when you are having thousands of collisions, or millions in Rob’s case,” Lieberman says. “You cannot be a thumper and a great runner.”

In London, Courtney Kipps had observed something else about Young’s footfall. When the typical recreational athlete runs on a treadmill their feet seldom land in the same place. With Young, the landing map looks like a single pair of soles – he strikes the same spot every time. This is a strong ­indication of running efficiency; Young uses no additional energy in trying to balance or push off.

But other results are “remarkable for how unremarkable they are”, Kipps says. Young’s VO2 Max – a measure of how much oxygen a person’s body can use during exercise – is average for a three-hour, 30-minute marathoner. (His personal best is two hours and 41 minutes, but most of his runs are slower.) His anaerobic threshold, the point at which lactic acid starts to accumulate in the muscles, is good, but not exceptional.

And so science alone cannot explain Young’s ability to run and run. His mindset may. Kipps notes that Young never shows long-term concerns; he is always enjoying the moment. “It’s like kids who don’t know danger or fear – they have no limits. That only comes later. Rob has a brain that does not all allow him to say: I cannot do that,” Kipps says.

And then there is his high pain threshold. Kipps and the other medical experts who have worked with Young wonder where it comes from. Does he not feel pain, or does he just ignore it? Is it genetic, or is it all down to what he experienced as a boy, and how he trained himself to deal with it?

Young himself has few answers. “If you look at many ultrarunners, they have come through something,” he says. “Maybe learning to control pain as a kid allows me to cope better now.”

He knows, for instance, that when one part of his body is sore he can apply hurt to another – pinching, biting his lip – as a distraction. And that he can trick his brain: 20 miles in to a run he tells himself he has only covered five miles, and thus should feel fresh.

This he can say for certain: “I run with my heart and my mind.”

****

How far can a person run without sleep? Two hundred miles? Three hundred miles? Surfing the internet, Young realises it’s further. In 2005 Dean Karnazes, one of America’s best-known ultrarunners at the time, ran 350 miles through northern California. Back from the US, Young makes plans to run 500 miles in one go. He plots a roundabout, 420-mile route from Eastbourne to Birmingham, which he reckons will take him four days. If he times it right, he’ll then be able to line up for an 80-mile race.

It will be a shoestring attempt; he and Joanna have just £80 between them when he leaves to catch an early train to Eastbourne on Tuesday 21 July 2015. She keeps £40 to get her through the week, and Young takes the rest to buy food along the run. If he has to sustain himself on bread and jam, he will.

The first 24 hours go well, as he clocks 130 miles. The next 150 miles are more of a slog. As he nears 300 miles, he is in a bad way. It is the middle of Thursday night. First his legs feel dead, then his shoulders, lower back and arms. Pain shoots up through his shins, knees and thighs. His head feels as if it will explode. He stoops and shuffles like an old man; a mile takes 20 minutes.

In the middle of the road he spots a seal, and then human outlines in the distance, glowing white. He was expecting to hallucinate at some point, so he doesn’t feel panic. But the two members of his rotating support team do.

“Both of us on the crew were nearly 50 years old and responsible people,” says Ben Thornton, a friend who knows Young well. “We kept saying to each other: should we be trying to convince him to stop?”

Thornton rides ahead on his bicycle, finds a petrol station with a vending machine, and fills up several drinking bottles with black coffee laced with sugar. Young downs a bottle, and soon after runs a mile in less than six minutes. When he is again spent, he drinks more coffee. In this way he keeps going, edging ever closer to the record as the rain comes down. After pausing for a roadside game of quoits, he passes the 350-mile mark, celebrating with a McDonald’s burger and more caffeine.

The rain gets heavier, and the Friday evening light fades. Young vomits. His face turns bright red and feels like it’s on fire. His throat closes up. The support crew calls for an ambulance. Paramedics check his heart rate and, fearing he might be having a mild heart attack, say he should go to hospital. Young tries to dissuade them. “What if you just drive along as I keep running, and when I collapse you restart my heart and get me to hospital?” he asks.

The run is over. He has covered 373.75 miles in 88 hours. Six weeks later, he is at it again, running 2,250 miles around the UK in 25 days with Adam Holland, a British ­ultrarunner, to raise money for a charity promoting peace in Kenya.

****

It’s January 2016, and Young is back from his run to Hammersmith. As Alexander plays with toy trains at his father’s feet, Joanna serves the cauliflower soup. They chat about how their lives have changed over the past 21 months, and laugh at how bad Young is at keeping his telephone charged. “For Joanna to put up with me . . . It takes a lot,” he says. “But now we are good.”

When Peter Wells, Young’s foster carer, visited at Christmas he gave him two pieces of advice: make sure that you look after Joanna, and don’t do anything too silly with your body. Young intends to honour the first of those. Having a stable family of his own helped him move on even more from his past. Though he will never forget – he still has a small white scar on the outside of his right knee and another on top of his right foot, from the fork and the nail – he made the decision in his teens to forgive his father. (His father was in jail then and remains there today, Young says.)

“I got to a point where I was no longer scared of him, or controlled by him. There was no shame, and I did not want the anger to hold me back,” he says.

Sponsorship by the sportswear company Skins – he also gets modest support from Lucozade – and a small advance for his autobiography have relieved some of the financial pressure, but to cover the rent he still needs more endorsements, which means planning new feats of endurance.

His first big event this year, assuming he can find the cash for a flight to the US, will be the Vol State 500K Relay, a 314-mile adventure race that he will do with Adam Holland, starting in late April. Then he’ll embark on his main challenge, perhaps his most ambitious yet – to break the transcontinental record for running across the United States from west to east. Unlike the Race Across USA, which had set stages each day, this will be one long run against the clock.

The record has stood since 1980, when Frank Giannino, Jr ran the 3,100 miles from San Francisco to New York in 46 days, eight hours and 36 minutes. If Young betters it he will receive widespread coverage in the US, improving his profile and that of his charity appeal. (He says he has raised more than £200,000 to date for Dreams Come True, Great Ormond Street Hospital, the NSPCC and other organisations – and hopes to set up his own charity one day.) “Physically, other guys are better than me,” Young says, referring to failed attempts by other ultrarunners to break Giannino’s record. “But I have the ability to suffer and cope when others break apart.”

He also wants to test himself in more hostile environments. Last year, he met the explorer Sir Ranulph Fiennes and discussed solo expeditions. When Fiennes mentioned a North Pole crossing that nobody had yet done, Young said: “Get me the gear and I’ll try it.” There are great mountain ranges to be traversed, vast rivers to be swum. When he talks about the risks, Joanna looks up, and he lowers his voice. “I am slowly realising that this is who I am. It might lead to death but you cannot change when you have found who you are.”

****

The man is running. It is now late February. He is lighter, stronger. Any day now he will become a father for the third time. Entering Richmond Park he veers off the gravel trail, across the grass, through a knee-deep river and up the bank. Ahead is a hilly area covered in trees and webbed with muddy footpaths where he likes to train, doing repeats of a figure-of-eight circuit.

Charging up a sharp ascent, he tumbles, landing heavily. In a flash Rob Young is back on his feet, legs pumping. He does not look back to see what made him fall.