After a successful career in karting, Kevin, son of 1994 British F3 Champion and Stewart F1 driver Jan Magnussen, made the switch to single-seaters in 2008, winning the Danish Formula Ford championship with an impressive record of 11 wins, 12 podiums, 6 pole positions and 10 fastest laps.
The following year, he graduated to Formula Renault 2.0, finishing runner-up in the Northern European Cup and seventh in the Eurocup. In the NEC, he scored one win, 12 podiums and two pole positions - achievements that earned him the 'Rookie of the Year' accolade.
In 2010, he moved into German F3, impressing immediately by taking victory in the opening round of the season. It was the first of three victories on his way to securing third in the championship and once again being named 'Rookie of the Year'.
Kevin also joined the McLaren Young Driver programme in 2010, dovetailing his racing activities with training and development work with the legendary F1 team with which his father made his F1 debut - a one-off outing with the Woking team in the 1995 Pacific GP at the Aida Circuit where he replaced Mika Hakkinen who was recovering from appendicitis.
In 2011, he moved into British F3, building upon the successes of the previous season. He finished second in the championship after securing seven race wins, six pole positions and eight fastest laps.
As a result, his F3 team, Carlin Motorsport, signed him up for 2012's World Series by Renault 3.5 series. As a rookie, he won once and took three further podium spots, but the year helped him sharpen his teeth before a full assault on the WSR title in 2013.
With a year's experience under his belt, Kevin underlined both his speed and maturity, slowly tightening his grip on the title, before underlining his supremacy by dominating the series' final two rounds.
It was this blend of assurance, maturity and potential, as well as a pair of stunningly impressive testing outings at Abu Dhabi and Silverstone, that helped him land the drive with McLaren for 2014.
As the first Dane to start an F1 race for a decade - Nicolas Kiesa raced for Minardi at the tail-end of 2003 - a nation's gaze was directed towards him when he lined up on the grid for the season opener.
In pre-season testing the MP4-29 was strong, not least due to the fact that Mercedes had clearly mastered the new formula. Kevin topped the overall times at Jerez and was third overall in the opening test in Bahrain. By the end of the final test he had slipped to sixth, but no cause for alarm.
The season got off to the worst possible start when Kevin and Button finished second and third in Melbourne, courtesy of Ricciardo being disqualified for fuel irregularities.
We say 'worst possible start' because basically this is as good as it got. Though there were some good performances, they were few and far between and never totally convincing. Furthermore, whilst clearly running the best power unit on the grid the spectre of Honda and the 'ghost of season to come', continually hovered over the Woking outfit.
In total the Dane score points in twelve of the season's nineteen rounds, but by the end of the year had totalled around a third of the point scored by his iteammate. Worse, though considered "lightning quick" Kevin was trounced 10-9 in qualifying.
For the most part, Button had the measure of Kevin, the Briton's consistency and experience winning out, particularly in the second half of the season, whilst, other than Russia, the Dane's challenge all but fizzled out.
On December 11, following weeks of speculation, it was confirmed that Fernando Alonso was returning to Woking, the team finally also putting Button (and his fans) out of their misery by confirming the Briton for a sixth season.
Kevin was retained as test and reserve driver, whilst Stoffel Vandoorne was also kept on the books, a fact that would not be lost on the Dane.
Whilst nobody really expected the latest incarnation of the legend that was McLaren-Honda to sweep all before it, rekindling those glory days of the 80s and 90s, surely nobody expected it to be the unmitigated disaster that it was.
The MP4-30 managed just 12 laps over the first two days of pre-season testing at Jerez, and when Alonso completed 32 laps on the third day there was a collective sigh of relief in the McLaren camp, but then came Barcelona.
On the final day of the first Barcelona test, the Spaniard crashed heavily at T3 in circumstances that have never been explained. Indeed, it was the statements then denials that first got people wondering what on earth was going on, a question that was oft repeated over the course of the year.
Ruled out of the opening race of the year, Alonso was replaced by Kevin, who - like his teammates - had had little significant time in the car. Starting from last, the fact the Dane's car broke down on its way to the grid tells you all you need to know.
With Alonso back in the car for the remainder of the season - even though he might well have wished he hadn't been - Kevin focussed on his duties a reserve which mostly meant the simulator.
As the year progressed and Vandoorne looked set to secure the GP2 title, Kevin was the centre of much speculation, and whilst he was said to be under consideration for a 2016 drive the team ultimately decided to retain its 2015 line-up.
Despite being likened to Ayton Senna by Trevor Carlin, Kevin was informed his services would not be needed by McLaren, the Dane given the news on his birthday... by email.
In mid-January, amidst talk that Kevin was said to be considering a number of options including WEC, rumours linking him with the 'new' Renault team began to emerge and it was revealed that the money from PDVSA was overdue, thereby putting Pastor Maldonado's seat in jeopardy.
Venezuela, already in the midst of its worst recession in living memory, the global oil glut, and the resultant effect on prices, inflicted further pain. On February 1, Maldonado took to Twitter to announce that he would not be on the grid in 2016 and with just 48 hours before Renault revealed its new livery and driver line-up, it looked as though Kevin was heading back to the grid.
It's ironic that Kevin was leaving McLaren for Renault, for both teams found themselves with mountains to climb.
The late purchase of Lotus by Renault not only had an impact on the car - the French team forced to use a 2016 Lotus built for a Mercedes engine and using 2015 components - it meant that the manufacturer headed into its 'debut' season almost totally unprepared.
In the final years of Lotus the facility at Enstone had been allowed to fall into disrepair, the workforce seriously depleted, machinery and licenses out of date and all manner of other problems greeted the new owner... and its drivers.
In all fairness, Kevin did the best with the equipment he had at his disposal, which wasn't much. If proof were needed of how bad things were for the Enstone outfit, think about the fact that despite using the same engine as Red Bull, the Austrian team scored two wins and amassed 468 points while the French outfit struggled to score 8.
The Dane did his best, though this often meant overdriving the car. Indeed, for much of the season he appeared to be trying too hard, and consequently paid the price.
In Bahrain, having been forced to start in the pits, he drove a determined race and was unlucky not to make it into the points, the Dane finishing eleventh.
Avoiding the first lap madness in Russia, canny strategy saw the youngster undercut (future teammate) Romain Grosjean to take seventh, giving the team its best result of the year.
Having out-paced his teammate for the first half of the season as Palmer gradually began to find his feet so Magnussen pushed ever harder. Sadly, more often than not this led to mistakes.
While he was the innocent victim of Daniil Kvyat in Monaco - who wasn't at some time or another - his overdriving proved costly in Canada, Italy and Belgium where he crashed heavily whilst battling his teammate.
At times his driving bordered on desperation, surely it was no coincidence that in the wet he was regularly among the first to make the switch to slicks, a risky move at the best of times but even more so when at the wheel of a car with the downforce issues of the Renault. Indeed, in Britain and Brazil the early switch to slicks proved costly.
For 2017 Kevin headed to Haas to join Romain Grosjean, a team that, like Renault, was having to find its feet.
With Esteban Gutierrez proving a major disappointment in 2016, the American team was looking to Kevin to contribute as the team moved forward. Indeed, having demonstrated not only that it meant business but that it is serious about making progress, 2017 represented Kevin's chance to shine.
Though it usually failed to impress his colleagues, Kevin's determination to live up to his Viking heritage with his race-craft more often than not won the fans over in 2018.
Time and time again he went into battle and while sometimes it worked in his favour on other occasions it didn't.
Sadly, it was mostly due to his dire qualifying performances that he was left with a mountain to overcome next afternoon, the Dane not once making it into Q3 while teammate Grosjean did it four times. Indeed on two occasions while Grosjean made it into Q3, Kevin was eliminated at the first hurdle.
Consequently as he attempted to work his way through the field there were clashes aplenty. Indeed, the first race of the season saw him suffer suspension damage following a first lap encounter with Ericsson.
In the months that followed, Kvyat, Hulkenberg and Alonso, three drivers who themselves don't mind rolling up their sleeves and getting stuck in, were among those enraged by Kevin's antics.
In Hulkenberg's case, Kevin's verbal response, made it clear that he wasn't out there to make friends and didn't intend changing his tactics any time soon.
Fact is, when it worked it worked and we appreciated the Dane for it - such as his move on Massa at Suzuka - but more often than not it was unnecessary and merely cost Kevin and his team valuable points.
In addition to his aggressive driving, the Dane was also aggressive when it came to tactics, almost always the first to switch tyres in difficult conditions.
Indeed, as the Dane continued to confound (and entertain) arguably his best performance of the year came in Mexico, a circuit where Haas fully expected to struggle, as confirmed by Grosjean's 15th place... two laps down on the race winner. Starting from the back row Kevin soaked up the pressure not only from regular sparring partner Alonso but a certain Mr Hamilton, and dealt with both admirably.
His best result of the year was Baku, but while not wishing to deride his efforts that particular event was more lottery than race. If Mexico was the high point, Spa was the low, the youngster finishing 15th while his teammate finished in the points.
Retained - and rightly so - for 2018, we opined that if Kevin could improve his qualifying performances he should leave himself with less of a mountain to climb on Sunday. Then, assuming he could channel his aggression, he might be able to feature in the points more regularly and put his teammate under more pressure.
In fact, not only did he score on both counts – claiming more points and putting Grosjean under pressure - he also improved in qualifying, and was ultimately out-qualified by his teammate 11-10.
However, much like Hulkenberg at Renault, Kevin had a hit and miss season, and really should have delivered more. Admittedly, his cause wasn't helped by a team which, though taking a significant step forward, often, though its relative inexperience, meant it failed to fully deliver.
No clearer was this shown than in the season opener in Melbourne, where Kevin (running fourth) and Grosjean (fifth) were eliminated following unsafe releases, while at Austin he was stripped of ninth for a fuel infringement.
Bouncing back from the disaster that was Melbourne, Kevin gave himself and his team the ultimate confidence boost by finishing fifth in Bahrain and claiming sixth in Spain just a few weeks later.
However, a strong mid-season spell was followed by an inexplicable lean period in the second half of the year when there were times one wondered if Kevin was still racing.
Other than his unexplained loss of pace in the second half of the season - during the races and in qualifying - over the course of the year Kevin was once again embroiled in a number of questionable incidents with rival drivers. Also, at a number of races, not least Monza and Singapore, he was inexplicably off his teammate's pace.
That said, the Dane's two DNFs were not down to him, and over the course of the year he showed impressive consistency.
If Grosjean could keep his seat it was only right that Kevin be retained also. However, in 2019 the Dane had to not only show the pace witnessed during the first half of 2018... he had to maintain it.
Eighth in its debut season, eighth again in season two and then a convincing fifth in season three, much was expected of the American team in 2019, but it was not to be.
In pre-season testing and at the season opener, it really looked as though Haas was in business, Grosjean and Kevin claiming sixth and seventh in qualifying. However, while the Dane finished sixth in the race, his teammate was to suffer a repeat of the same unsafe release that had sidelined both drivers just twelve months earlier, a slipshod error that signalled the team is still not learning from its mistakes.
Sadly, in many ways, Australia was as good as it got.
While Kevin, in particular, continued to perform brilliantly in qualifying, making it to Q3 in five of the first six races, everything fell apart on Sunday, for though most teams had a window in which their tyres were at an optimum, at Haas the window was miniscule.
In Bahrain, Kevin was close to pulling off the upset of the season, when he almost out-qualified Max Verstappen, but next day the Dane was left speechless and visibly shocked after slipping down the field and struggling to finish 13th. More disappointment was to follow in China and the Azerbaijan.
Though the team introduced an upgrade in Spain it only made matters worse, and it wasn't long before it became clear that the American team had a fundamental issue. As the team struggled to understand the problem, far less solve it, all manner of fixes were tried, with Grosjean reverting to the Melbourne spec.
Later in the year as the struggles got worse, Steiner admitted that he should have listened to his drivers as the team continued with its strange 'pick and mix' approach to its aero package depending on the circuit.
Soon, Saturdays, like Sundays, were a write-off, and much like 2018, Magnussen appeared to lose faith, though this time around it was understandable.
"You go into the graining phase, and then when we go into the graining phase we cannot get out of it anymore because our tyre then gets too cold and then we are done,” said Steiner in Azerbaijan, just four races into the year, but with the Achilles heel of the VF-19 already clear. "Then we slide around."
Despite his understandable disappointment on his day Kevin could still step up to the plate, his qualifying performances in Monaco and Austria quite sublime.
While the equipment at his disposal meant he was unable to mix it on Sundays, usually a sitting target for those he had out-qualified to pick him off, he dominated his teammate on a regular basis.
2020 is not only the last year of Kevin's current contract with Haas, it is also the year in which the American outfit could opt to call it quits.
While, for the most part, Grosjean has disappointed, we have never seen Kevin in a regularly competitive car. In 2019, there were times the Dane appeared close to giving in, such was his frustration with the wretched VF-19.
Let's hope that for all concerned, that the VF-20 is a significant improvement.