'It's a big moment," says Karl Bushby, who has had plenty of big moments in his life. He is recording himself on his phone for social media. "We're in Dover, and I'm about to have my first fish and chips and mushy peas in 28 years. Mushy peas, my God, I forgot they even existed!" He points his phone at the plate in front of him. "It better be good." And he tucks in. "Mmmm. See, this is a big chunk of fish and a decent bit of batter, and that's something you don't see in other parts of the world. I mean, come on! That. Is. Fish. And. Chips! You see, Britain is special."

It has been two days since Bushby swam the Channel to return to England. Tomorrow, he'll start the walk home to Hull for the first time since he left in 1998. He hopes to get back on 1 November, the same date he set off all those years ago.

Although Bushby is a man of military precision, timing is not one of his greatest traits. When the former paratrooper left the army, aged 29, to walk the world, he planned to be home 12 years later. What accounted for the extra years? "The real world. You can't account for financial crises, pandemics, visa bans, wars and the bureaucracy you have to deal with. It took 28 years because of the rules and because we refused to compromise on the route." I ask what he means by "we"? He smiles. "It's the royal we. Me and the Beast."

Ah, the Beast. That's the customised golf trolley he travelled with, containing essential survival equipment, camping supplies, electronics and food. The original Beast lasted three years before it broke down and had to be put out to grass. The Beast 2, an upgrade he built in Nicaragua, has survived 25 years.

Rather than circumnavigating the globe, which is impossible without transport, Bushby decided to walk about as far as he possibly could. As his starting point he chose the southernmost city on the South American continent, Punta Arenas in Chile (53 deg S), and planned to make his way across the Americas, Asia and Europe back to his home town, Hull (which is, at 53 deg N, the latitudinal mirror image of Punta Arenas). He was guided by two simple self-made rules: he could use no transport to advance, and there was no going home until he arrived on foot, mission completed. If he had to make a detour or pause his trip, by force or by choice, he would use transport, but always restart at the exact spot where he had stopped.

Bushby has walked approximately 36,000 miles (58,000km), breaking the record for the longest unbroken foot journey and far exceeding the 25,000-mile circumference of the world. When he gets home he will be the first person to have walked continuously across the world, visiting 29 countries. En route, he broke other records (as part of the first teams to complete the crossing of the Bering Strait, from Alaska to Russia, on foot in modern times, and to swim the Caspian Sea, from Kazakhstan to Azerbaijan). He has also almost died, spent years stuck in Mexico because he lost his sponsor, been convicted of being a spy, been held in custody in Russia and sentenced to deportation, been threatened at gunpoint and faced the prospect of predation by a polar bear. To many he's a hero. To some, he's a reckless chancer.

We meet at the White Horse in Dover, its walls graffitied with the times people have taken to swim the Channel. Bushby looks at them and says they show what an amateur he is. It took him 20 hours over three days to swim the 21 miles (34km) on his back. "There's one over there who did it in 10 hours. Swimmers normally go twice the speed I did. Real swimmers are in trunks, caps and a pair of goggles. I've got a wetsuit, fins, paddles for my hands, a flotation vest, neck flotation. I don't call what I do swimming, out of respect to real swimmers. I call it 'floatimming'."

Bushby looks fit in the way that people who take regular constitutionals do. His face is tanned from the sun and the wind; his hair is still blond, his eyes sea blue. But he is also very different from the man who set out three decades ago. At 29, Bushby was skinny with shoulder-length hair – a dead ringer for Kurt Cobain. Once the media started reporting on his "Goliath expedition", a joke/conspiracy theory went round that the former Nirvana frontman wasn't really dead, he was just walking the world using the pseudonym Karl Bushby.

Today, at 57, he is strong, with a bone-crunching handshake, a fuller face and a hint of middle-aged spread. He says people don't expect him to look the way he does. They either imagine him as Gandalf, with a white beard down to his knees, or as a ripped athlete. "Everyone's saying: if he's been walking 28 years, why does he look so fat? But most of the time I'm eating out of gas stations, burger bars, sitting somewhere for three months waiting for a visa, getting older, eating biscuits and cookies."

He has brought along a friend, Angela Maxwell, a 44-year-old American who spent six and a half years walking the world, some of it alongside Bushby. She also swam the Caspian Sea with him over 31 days in 2024, accompanied byAnastasia Boborykina and Abdurrahman Rustamov, two young Azerbaijani champion swimmers.

Maxwell tells me that in many ways she and Bushby are different, but they are similar in important ways. "We're both introverts, even hermits in some way. We like our autonomy." Maxwell is a funny and talkative introvert. Bushby is a more conventional introvert – quiet, understated, dry.

Bushby grew up in a military family. His father, Keith, is an SAS veteran who spent 24 years in the British army, and his younger brother, Adrian, is also an army man. His mother, another Angela, worked in a factory.

School, Bushby says, was a "living hell". Dyslexic (though undiagnosed), he was branded as "thick", and found solace in birdwatching. He left school at 16 with no qualifications and joined the junior Parachute regiment. But he struggled with the physical demands, and took five attempts to pass the gruelling P Company training before eventually joining the 3rd battalion of the Parachute regiment. Some mocked him for his repeated failures, but others were impressed by his tenacity. "Normally, they'll allow you two or three attempts." Why did he get five? "Because I wouldn't quit … that was probably one of the first signs. I just won't let go. I'm a bit of a rottweiler." He says he thinks he may be on the autistic spectrum.

Bushby remained an outsider in the paras, not least because he didn't like booze. "I was never a beer drinker. And that's very bad news in the army. Very difficult. It can be a problem." Throughout his military career, he felt his peers didn't trust or respect him.

In his early 20s, stationed in Northern Ireland, he married a Belfast woman, yet another Angela. Five years later, when they were living in Hampshire, they divorced. She returned home to Belfast with their young son, Adam. At the time, servicemen were only allowed into Northern Ireland if they were serving there, so Bushby was effectively separated from Adam.

There was another thing gnawing away at him. A professional, or existential, crisis. The world was at peace, which was catastrophic for those who had joined the military hoping to see action. Between 1990 and 1995, the British army was downsized from 160,000 to 120,000. Bushby kept his job, but he was bored and restless. "We were not being used. There was nothing going on. I was one of those guys looking for other challenges in life. We were all disillusioned because of the lack of action – the "peace disease", as the Chinese refer to it. It's hard to keep an army in combat fighting conditions when there's nothing to do. As young soldiers, you're up for the fight, and you end up in Northern Ireland on sentry on a gate every day. It's not very appealing."

Ever since childhood, he had wanderlust, a longing for new horizons. "I used to dream about great big journeys on foot. I started drawing lines on maps, and the conversation spread between friends." Had he ever done a big journey before? "No! ."

In his mid-20s, he got a birthday card from his father that mentioned a group of SAS soldiers who were discussing the possibility of walking from London to New York. That was an epiphany, Bushby says. There was a map on the wall, and he took a black marker pen and drew a line from the UK to Europe, through Asia, over the Bering Strait. Then he thought: why stop in New York? So he extended the line down to the bottom of the Americas. He knew there were a few obstacles, but as far as he was concerned, the whole world was connected if he could get over the Bering Strait. Not that he knew what the Bering Strait was, or that nobody had successfully crossed it in modern times, since it had broken down into treacherous blocks of ice. (Some scientists believe Paleo-Indian people may have crossed from Siberia into Alaska 17,000 years ago, when ocean levels were lower.)

For the next couple of years Bushby studied the route, working out how his dream could be turned into a reality. It meant swotting up on the subjects he'd flunked at school – maths, physics and geography. The more he studied, the more he told people he was going to do it. "Nobody took it seriously when I said I wanted to walk around the world. It was like, 'Karl just had this crazy batshit idea of spending 12 years walking around the world. Yeah, whatever!' That was the response from everybody, and that fuelled the fire. But I would look at the map, and think of what kind of life that would be. I couldn't let go of that."

He was also motivated by poor mental health. He was a keen distance runner, and if he went a single day without running, he suffered anxiety attacks. It got so bad that he saw a behavioural psychologist. "It dominated my life. It really did."

Perhaps the biggest motivation of all was an overwhelming sense of his own mortality. "I took death seriously. You're dying, you've got one life, and what are you going to do with it? That really resonated with me."

Once Bushby had made up his mind, he accepted that he would never see his son growing up. If everything went to plan, Adam would be 20 when he got back (as it is, he is 36).

"That was a difficult decision," Bushby says. "But the way I squared that circle was, 'How would I be worth something to my son?' Would I be worth more to him by doing something on this scale?'" He doesn't sound wholly convinced by his argument.

n 1 November 1998, Bushby set off from his mother's house. He flew to Chile, hitching a lift to the Falkland Islands on an RAF military transport flight. From there, he took a short civilian flight to cross over to his official starting point in Punta ArenasChile. He set off from there with $500 (then equal to about £300) of savings and the Beast, speaking no Spanish, and was met immediately with a ferocious environment on the Patagonian steppe. Hurricane-force winds were raging. The freezing gales forced him to lean at a 45-degree angle just to stay on his feet, for days at a time, while dust and grit pelted his face. He experienced suffocating altitude sickness, breathing difficulties and starvation.

Bushby soon realised that pushing his way across the wind-lashed, bone-dry plateau was a death sentence. He altered his route to cross the Andes and headed west towards the coast. The terrain was still hostile (at one point he survived on one banana for three days), but he began to meet people who transformed his view of humanity. When he needed warmth or food or simply contact, they provided it.

"There are so many examples out there. Where would we be without some of the help we've had? Just the simple stuff. You'll find people living in shacks on the side of the road built with car parts – hoods and doors taped together. These people are just scratching out an existence, but they'll give you a bowl of rice and water."

By now he was beginning to speak Spanish, but often he didn't even exchange a word with those who helped him. "I was walking through the Atacama desert in Chile. You've got one main highway, Route 5, so the truckers and coach drivers get to see the same guys over the months as you're inching forward, and eventually they become your support network. You're now in the driest desert in the world, and those trucks are passing me fruit, and bottles of water get thrown out for me. I don't know who's in that truck, but they're looking after me."

He tells me about a Chilean family who would regularly drive hundreds of miles to give him provisions and spend time with him. Then there was the stranger who drove up to him on the highway, asked if he was Karl Bushby, and handed him an envelope containing a huge booklet of food vouchers for meals at the German-Chilean restaurant franchise Bavaria, whose outlets are dotted along the highway. The man, Michael Bier, also gave him $100 on condition that Bushby hand-deliver a postcard to a friend in Vienna, which he eventually did – 27 years later.

Bushby admits he had a mean-spirited view of humankind before the walk. "Twelve years in the army, you don't get to see the best of humanity, but the kindness of strangers …" He trails off. "I always say 99.999% of the people I met represented the very best of humanity. Every country has been the same."

And he met them just when he needed them most. In 2000, in Peru, he caught a severe stomach infection along with multiple secondary bacterial infections that left him fearing the worst. "This guy stopped me one day and said: 'Come and stay with us when you get to the next town.' His wife just happened to be a doctor running an analysis company. I walk in, sick as a dog, they take blood and samples, put me in bed for the week, quadruple-dose me on antibiotics, get me back on my feet and don't want anything for it." He shakes his head in wonder. "Another miracle," he says.

he one time he did meet with the 0.001% of people that weren't the best of humanity was in Colombia. "At the time, the country was a lawless mix of insurgency, counterinsurgency, drugs and counternarcotics intelligence agencies. There was even MI6 chasing the IRA, who were teaching the leftwing guerrillas how to make bombs. Nobody trusted anything or anyone. I was a blond-haired gringo in the kidnap capital of the world. Pretty stupid."

But he fell in love with the country and with a woman called Catalina, whom he was with for seven years. "She struggled because there was no country north of Panama that would let her in, because she was a single woman and Colombian. She was a civil engineer, very intelligent." But she couldn't cope with the instability of their life. "Eventually, she was headhunted by an energy company in Spain and met someone there." His heart was broken – not for the last time.

He left Colombia in about 2000 via the notorious Darién Gap, a 60-mile (97km) stretch of dense rainforest, swamps and mountains that served as cover for guerrilla groups such as the leftwing Farc and the rightwing AUC on the border between Colombia and Panama. The gap is the only break in the Pan-American highway (the world's longest motorable road), and Bushby had to cross it because it was the only way of reaching Panama. He dressed as a vagrant to make himself less conspicuous, with maps, compasses and essential medicines stitched into secret pockets in his clothing. At times, he backstroked his way down rivers, disguised as detritus.

Was it scary? "Oh yes, absolutely. I found myself at gunpoint a few times. People are often executed when caught by the revolutionary armed forces."

What happened when he was held up at gunpoint? Again, he says he was lucky. "These situations weren't that bad. I've been held at gunpoint by someone who bumped into me in the dark and was scared. And normally it's the police or army. There was a situation where you find yourself being confronted by a rightwing paramilitary organisation." By now, his Spanish was decent. How did he talk his way out of being shot? "Keep smiling, play it down. Don't get angry. Just a smile will get you through so much. Just defuse, defuse, de-conflict and you're going to be all right."

He was also helped by a file he carried, documenting his journey. "Luckily for me, when dealing with those people, I had all these copies of newspaper clippings from South America. With them I could talk my way out of anything."

Between 2002 and 2005, he travelled through America, eventually reaching Alaska, where he confronted the most dangerous part of the expedition. To get from the US to Russia, he had to cross the Bering Strait, a narrow 51-mile (82km) frozen waterway connecting the Arctic and Pacific Oceans. The problem is that it is no longer all frozen. Bits are continually falling off as ice turns into sea and back again. Nobody had ever successfully crossed from Alaska to Siberia on foot (going the other way is easier because you are moving with the natural drift of the ice, whereas going towards Russia means you're fighting against the ice). Bushby teamed up with the French-American adventurer Dimitri Kieffer – neither had experience of Arctic conditions.

A BBC crew went out to film the mission, but had to return to base early because the trek was too dangerous. In the introduction, the presenter, Morland Sanders, said: "Karl Bushby, the ex-paratrooper on a mission that nobody has ever done before. To walk, swim, stumble across a semi-frozen sea. The chances are he won't make it across alive." Bushby told Sanders that throughout his life he'd constantly dealt with failure, and now he was out there proving himself. "Some people might think it's ludicrous, some people might think it's irresponsible, some people out there will understand the way I feel. Some things in life are worth dying for." And he and Kieffer almost did.

At one point, the thin ice shelf beneath them gave way, and their 90kg supply sleds plunged into the sub-zero ocean water. Losing those sleds meant certain death from starvation or hypothermia in -30C temperatures. In terrifying footage filmed by the two men, we see them pulling the waterlogged sleds back up on to solid ice before they could be sucked under the shifting ice packs.

They also came face to face with a polar bear. "We tried to scare it off, but all we had were fireworks and they were useless. So eventually we inched our way towards this bear. It stops and it's looking at us. If it wanted us, we're dead. There's no escape at this point. It stood up to get a better look at us and it just rose into the sky like a freaking skyscraper. It was horrifying. They are . Massive." The bear stared them out, then wandered off. He exhales loudly, the relief still fresh. "There was just no way you're getting away from that."

Although the conditions were almost perfect, it looked as if they had insufficient food to last. Then, on one amazing day, they managed 12 miles, and after 14 days they made it across, just before running out. Another miracle, Bushby says. How did it feel to have made history? "It's a pretty good feeling."

On reaching Siberia, the pair were arrested on suspicion of spying, charged and convicted. The authorities wanted them to serve a minimum of five years. In the end, they relented and sent them back to Alaska.

But it wasn't any of these challenges that Bushby found toughest to deal with; it was walking away from love. Or love walking away from him. In Mongolia, he met a Japanese woman called Rika. This relationship lasted three years, and again she eventually gave up on him. By that time, the pandemic had begun, and he had returned to Mexico because it was cheap to live there and Rika was in New Zealand. "She found someone else because we'd been separated for years. That is the hardest thing about this journey."

Did he never think love should come before the expedition? "No. Mission first," he says. "If you look at my diaries from Hull, I write about how I'm going to fall in love, how I'm going to keep going and how I'm going to get burned by this. It was in the prophecy and it was foretold."

To be fair, I say, you didn't make it easy for the women in your life. "Oh no. It was not the way to run relationships. But we knew we weren't going to stop," he says. I ask if he started referring to "we" to make him feel less alone. "I don't know, but now it's out of respect for everyone else who made this happen. I owe the world a lot. Don't ever think it's just me. It was never me. It is a 'we' thing. 'We' got me across the Channel to this beach in Dover. Me and a support network like no other. Before that, I just had the army behind me – now I have the world."

Bushby says he has led a selfish life. When he set off, he knew that if either of his parents died while he was away, he would not return for their funeral. When his son, Adam, almost died in a motorbike accident, he didn't return home. He tells me he's got a 12-year-old granddaughter he is yet to meet.

Does he get on well with Adam now? "Yeah, me and Adam are great." Did Adam ever ask why he hadn't been there for him when he was growing up? "No, he accepted it. In those early years, he had to deal with those questions: why is my father out there and not home? As he matured, we've managed to have those conversations. To his credit, he rolled with the punches. He understands his father, and he's one of my big fans."

Maxwell adds: "All adventure could be labelled selfish, because you're going to hike the greatest mountain and someone dies from an avalanche and they've got a wife and kids back home. You explore something and then you die in the sea. To have an adventure is self-centred."

"Totally self-centred," agrees Bushby. "This 28 years has been about keeping me. I have been the centre of my world. It has been about getting from A to B, looking after , giving the money so I can survive. Totally self-centred."

Has his family told him he's been selfish? "Not family, no."

"Everyone else!" Maxwell says, laughing.

"When you look at some of our great heroes, like Shackleton and Cook, they were the worst family men you could humanly imagine," Bushby says. "They abandoned families left, right and centre. That's the bit that people don't think about. Those people had families back home, and they never saw their father."

In his decades on the road, there were so many other adventures: 11 years struggling to get through Russia because of tough immigration rules and extreme weather; buying a caravan of camels, and the aborted plan to walk the camels along the Silk Road to Europe; being given a police escort through the heavily monitored Xinjiang region of western China because they also thought he was a spy.

There have also been periods of complete torpor. In 2005 he published a memoir after securing a substantial advance from Time-Warner, who had also agreed to sponsor the rest of his journey. When the financial crisis hit, they pulled out. He retreated to Mexico and just about got by for two years through working as a waiter and helping to run a boat-racing school. In 2010, the House of Cards showrunner Beau Willimon offered to sponsor him, and he returned to the road. Then the pandemic came and he was forced to hole up in Mexico for another three years.

And now, finally, he's back in England, heading home to Hull. How does he feel? Terrified, he says – in a way he hasn't been before. "My purpose for living is about to abruptly end." You seem very calm, I say. "My world's about to stop. I'm going to fall off the edge of the world in a minute."

" !" says Maxwell, as if he's being dramatic, although she admits that she struggled when she got home.

"I don't know how to do the grownup stuff," Bushby says. "I've got to get a job, I've got to grow up, and that's scary. When I get home, I'm going to be living in my mother's house." Is he close to her? "Not as close as I should be. There's a distance there." He says he'll have to put a lot of work into reconnecting. "It's going to get tough for me. My solution for this is to get busy. Find your passion, your other mission, sink your teeth into that."

He knows he has changed and believes he may struggle to fit in with his family now. "Coming from the UK, and a military family, I was very much on the conservative side." As a child he thought Britain was the centre of the world, but now he knows different. "My family is very patriotic and UK-centric. They are not lunatic rightwingers, but they're Brexit voters and all the rest of it. This is their environment. It's required for their jobs as soldiers and I understand the importance of that. But I'm not that guy any more."

Seeing the world can't help but change you, he says. "The world is an incredible place. People are worth all the effort. The species is an incredible thing. I've got a different attitude to the world; a slightly softer, left-leaning approach compared to some of the staunch politics in the UK right now."

Fortunately for him, Bushby is not returning to a vacuum. There is so much going on in his life. The great German film-maker Werner Herzog is making a documentary about his journey; there is a book in the works; talks are lined up. He could probably make a good living just giving speeches about his 28-year odyssey.

Could he see himself settling down with someone to a regular life, or is he post-relationship?

"That's a bit deep and dark," he says. "I would be open to a relationship for sure. Who wouldn't?"

"OK, here we go. I'll speak for Karl," Maxwell says. "Karl is the most eligible bachelor and adventurer for someone who likes the unknown. He is loyal, he's committed, he's a good lover and he's also committed to his mission."

Lover? Maxwell laughs, embarrassed. "I mean, he's a good love person."

"How do you know that I'm a good lover?" Bushby asks. "Wait. What?"

I ask them if they've been hiding something from me. "No," she stumbles. "No, I just meant a great lover of life."

"Yeah, that's what she meant," says Bushby. "That one. We're good friends. I like having her around. She makes life a lot more exciting."

"Wait a minute. You like ?" She sounds insulted.

"Yeah, we get along great," says Bushby. "You make life a lot cheerier."

"Yeah, all right," says Maxwell, semi-pacified.

The waitress removes our plates. Maxwell has left half her fish and chips. "I'll take that to go," Bushby says, pointing at her plate. He's used to scrimping.

"It does have tissue on it, if you don't mind," the waitress says.

"I've eaten worse," he says.

He is still thinking about how he's changed. Everybody in the UK seems so pessimistic about the future, he says, but not him. As a child he was a religious Christian, but then he became a militant atheist. Today, he says, he has more faith than he ever had – not in a god, or a prophet or the church, but in people.

"I'm the eternal optimist. Right now, everyone seems to think we're facing the end of humanity. Not me." He is betting on survival. "For me, I look at the species rather than a nation state."

Does he think he'll stay in Hull? "No," he says instantly.

Perhaps if he doesn't want to settle in Hull, after a rest he'll be ready for another walk?

"I wish he would," Maxwell says. "Can I answer this for him?"

"No!" he bellows. "The answer's no."

Maxwell bursts out laughing. 'He doesn't like walking. I love walking. He doesn't like walking."

Bushby nods. "For me, it was the journey in its entirety that was fascinating," he says. "It was trying to get from A to B."

You genuinely don't like walking, I ask, flabbergasted. "No, it's boring as hell." And now he's got the giggles. "It's really, really tedious."