The Dane, described by Sir Jackie Stewart as the greatest driving talent to emerge since Ayrton Senna, concedes he let himself down but his offspring can learn from his mistakes

The living room of Jan Magnussen's modest home in Roskilde, Denmark, is a celebration of his lustrous motor racing career. Burnished trophies appear to jostle for attention among the cabinets of helmets, beside a long row of racing suits, like headless ghost soldiers commemorating old campaigns.

This is also a shrine to the days of his curtailed Formula One career, which briefly promised to place him among the finest drivers of his time at the very pinnacle of motor sport. Jan could have, should have, been an F1 champion, but he faltered and was finished by the age of 25. Once described by no less than Sir Jackie Stewart as the greatest driving talent to emerge since Ayrton Senna, Magnussen admits he threw it all away, betrayed by his own naivety and lack of dedication, as well as the two teams he drove for, the leviathan McLaren and the novice outfit led by Stewart.

In Denmark's medieval capital, just around the corner from the gothic, sepulchral cathedral, the historic burial place for the nation's kings and queens, surrounded by ethereal mists on this January morning, Magnussen talks openly about the mistakes he made. And yet here, in the land of Hans Christian Andersen, there is a chance the fairytale could still come true.

At 19, Jan had a son, Kevin. Formula One fans will recall the toddler tightly grasping his hand in the paddock in the mid 1990s. Now Kevin has the chance to atone for the sins of the father after being plucked from McLaren's young driver programme to team up with Jenson Button in Formula One this season. At 21, he is hotly tipped to become the sport's most spectacular rookie since Lewis Hamilton blew in like a starburst in 2007 at the same team.

The young Magnussen arrives with a trumpet blast of expectation. "He is lightning quick," says the normally cautious Martin Whitmarsh, who hangs by a gossamer thread to his role as McLaren's team principal after last year, when they failed to win a single podium place for the first time since 1980.

Kevin, last year's champion of Formula Renault's 3.5 series, is so good that Sergio Pérez, despite a moderately successful debut season, was hastened out the back door to make room for him. The poignancy is not lost on Jan, for such bright hopes were once held for him, a driver who probably had even greater natural talent than his son, if not the same ferocity of targeted ambition.

After his own fall from grace, departing first McLaren and then the Stewart team after a season and a half in 1998, he secured enduring success as one of the world's outstanding sports car drivers – he was last year's GT champion in America's Le Mans series.

"I let myself down," Jan says, reviewing his brief F1 career. "I wish I'd had another chance but Kevin is where he is today because of what happened to me. He can learn from my mistakes.

"He is much more mature than I was at 21. In fact there are no similarities. He's super hardworking and much more organised than I ever was. I'm sure Ron [Dennis, his old McLaren team principal, who is once again in charge of the Woking factory's F1 operation] was frustrated with me. I was a smoker, I didn't train properly and was not at all organised. I was not ready for F1."

Jan and Kevin Magnussen at the 2012 young driver test in November at the Yas Marina Circuit. Photo: Grand Prix Photo

Jan had won three karting world championships by the age of 16, two junior and one senior, joined McLaren's young driver programme after winning 14 out of 18 British Formula Three races in 1994, beating Senna's 1983 record. He made his F1 debut for McLaren in Japan in 1995, when he replaced an ill Mika Hakkinen and came a worthy 10th, but never raced for them again.

As Dennis once said: "Jan was the most disorganised grand prix driver I've ever known. Once, we were at an airport and Jan had packed his passport into his suitcase. When he opened it, it looked like it had been packed by a four‑year‑old, like he'd just thrown everything into it, including his dirty washing, and none of his toiletries were in a bag. ''People like that are chaotic in their thinking,' I thought. 'There's no way he's going to make it.'"

It was, ultimately, Jan's decision to leave, in orderto have more racing with the new team run by Jackie Stewart and his son, Paul. "Ron advised me against leaving but I didn't hear a word he said. I just wanted to be a Formula One driver and I couldn't see myself in a McLaren with the driver lineup they had at the time. I should have stayed one or two more years, to have all the things I didn't have hammered into me by Ron Dennis.

"But McLaren were different then. Since then they have developed a fantastic programme for young drivers, which Kevin is benefiting from. It is a great team of people to have around you. He really is part of the McLaren family. They will take good care of him. For any situation, any question there's a guy to go to, someone to teach him. In my time, though, there was no coaching, no teaching the ropes. There was just me and they expected me to figure it out." Whitmarsh admitted some complicity on behalf of McLaren when he said: "Jan was a great talent that we didn't get the best out of – and when I say we, I mean Jan and us. His natural talent was phenomenal."

There was more frustration waiting for Jan when he joined Stewart's team in 1997. A bad car was replaced by something even worse in 1998 and Magnussen was sacked. He trusted his four-year contract a little too much, he says, not realising that in Formula One it is just a piece of paper. "My biggest problem was that I didn't have enough time in the car. It always blew up. We had a lot of mechanical failures. I remember sitting down watching the car burn on too many occasions."

A novice driver and a novice team was a bad combination. Once, humiliatingly, Stewart – pushing 60 at the time – took Jan for a driving lesson at Oulton Park and let it be known that he was the faster driver. "It made me look stupid. I have to drive my own way to be fast. I've great respect for Jackie but driving had changed a great deal in 30 years."

Jan, who looks more like Kevin's elder brother, will not be giving his son driving lessons. He has always believed in the primacy of the individual, although always within a team context. That explains why Senna is his all-time hero – and why he has so much time for today's Kimi "no crap" Raikkonen.

"Even when Kevin was younger, I didn't say: 'Turn here,' or: 'Brake there,' although my brother Erik did help. I remember, myself, that it's not always easy to accept good advice from your dad. Sometimes, when he was a teenager and I had some good advice for him, I gave it to somebody else, and he received it through the back door. He was two when he first got into a car, maybe less. I saw something straight away that was different. And he was interested in no other sport. He just wanted to be a Formula One driver."

Jan will miss Kevin's debut, in the first grand prix of the new season, in Australia on 16 March, because of his own driving commitments. "But I will get to eight or nine races, about half. Now Kevin is in Formula One I've thought a lot about how long my career will go on. I've got to decide whether I can focus on what I'm doing or whether I'd rather be with Kevin. But I don't want to be his manager. I want to be his dad, and that's it.

"We've become very close in the past two or three years and I want to be a good dad to him and be there when things go well but also stand right beside him when things go wrong. That's all I want to do."

Jan Magnussen and his son, Kevin, at the Jyllands-Ringen, Denmark, in 1998. Photo: Grand Prix Photo

There is a lambent nostalgia in Jan Magnussen's eyes as he gazes down upon his old McLaren helmet. "Kevin used to be the son of Jan Magnussen," he says with a grin. "Now, suddenly, I am the father of Kevin Magnussen."