“It was all about making the right decisions with his progression,” says Lagrue when asked about the most important contribution Mercedes made to Antonelli’s development. “Selecting the best environment, the best engineer, the best physical coach. We hired Sergi Ávila because we believed he had the right profile to help Kimi develop physically, because he was quite weak after go-karting. He was a little bird, so we had to work hard on this. We had to, and we still are, helping him on discipline, to be on time, not to spend too many hours pleasing everyone, because he likes to please people and sometimes we need to teach him to say no.

“It was a fast journey from go-kart to F1. You don’t usually have a driver who makes it in just three years. The most interesting part was the F2 season. It was a big jump skipping F3 and that’s the first time I saw Kimi dealing with difficult times. He was winning – not easily – before, but in F2 it was tough. The team had a difficult season, they were not adapting really well to the new car, but the luck we had was to have Ollie Bearman next to us because he was a good reference.

“Kimi worked super-hard with the team to get through this difficult period, becoming a clear leader, trying to find the solutions to get the team back in front and then start to win. This was a very nice experience with him because I never had the opportunity to see him deal with difficult moments. Last year in F1, we knew it was going to be difficult, probably maybe not as difficult as it was, and we needed to be next to him and to go through that process. That was necessary to make him the Kimi he is today.”

Antonelli’s driving style in F1 is striking. It’s aggressive, but controlled and subtle, reacting to constant microslides and dealing effortlessly with the barrage of tiny signals that trigger equally minuscule adjustments. To do that while producing consistency is a hallmark of excellence. Describe what you can see trackside from Antonelli in F1, and Lagrue recognises the style. It’s what he saw right from the start in karting, fine-tuned over the years working with Mercedes.

“It’s something we had to put a certain level of control into at some point, because he was sometimes overpushing a little and we had to teach him instead of always being at 110%, just be at 100%,” explains Lagrue. “He’s someone who will always try, he will try harder, he will explore a bit more than others where the limit is.

“Monza in his first FP1 [in 2024] was a clear example of this, and then you teach him to go back to something under control. And when he keeps everything under control, you have the example of the Brazilian Grand Prix last year, or the Monaco Grand Prix this year where he achieved something close to a perfect weekend [to win the race from pole position].”

“He’s someone who will always try, he will explore a bit more than others where the limit is”

That Monza public debut, which followed an exhaustive test programme, has gone down in legend after Antonelli shunted at Parabolica on his second flying lap. Antonelli was devastated, but it didn’t dent the team’s faith in him. And that wasn’t just public backing. Team principal Toto Wolff privately enthused about the speed Antonelli had shown earlier in the lap on which he crashed. “He’s not the person who’s going to let you down when things get difficult” is Lagrue’s verdict on Wolff’s support for Antonelli.

Wolff had long-since decided to promote Antonelli in a deal made public the day after the Monza crash, as he put it, “five minutes after Lewis told me that he’s going to Ferrari” in January. Antonelli was effectively put on an extended testing trial at that point, in tandem with his tricky F2 campaign. But Lagrue was right behind the choice.

“No, not for me,” he replies when asked if he had any doubts. “We made the decision early. We had almost a year, and in the worst-case scenario we will see if he is not ready and we can still call another driver and have a B-plan. But what we saw reassured us. Then Melbourne was extremely encouraging for a first grand prix.”

That fourth place from 16th on the grid in 2024 set Antonelli on the path to leading the world championship a little over a year later. So far, he’s shown little sign of struggling with the pressure, which Lagrue believes has “made him better” throughout his career. And the success on the way to F1 has somehow allowed him to treat his current situation no differently to what he’s experienced in the past. As Lagrue puts it, “he grew up with the culture of winning races and championships, and for him it’s no different in F4 than in F1”.

The stability in Antonelli’s ‘normal’ family background is cited as key to his outlook. His father Marco Antonelli, a racer in his own right, first put Kimi in a kart at the age of five. It’s impossible to evaluate the push-and-pull in terms of the extent to which Kimi motivated himself and what came from his father, but Antonelli Jr could never have made it to this level without force of personality. Lagrue and others in the Mercedes team, notably Wolff, have enhanced this, effectively becoming an extended family.

“What we saw reassured us. Then Melbourne was extremely encouraging for a first grand prix”

“With young drivers, you are dealing with every life situation – family things, personal things, the death of someone you have been close with, the first girlfriend, the first break-up,” says Lagrue. “We deal with that with all young drivers and that makes us very close to them. We are sometimes big brothers, second fathers, the shoulder they need sometimes, or the kick they need. I still see the same humble, passionate, hungry kid I saw a few years ago. He hasn’t changed. He’s maturing, of course, he’s developing, but ultimately he’s very humble. And I haven’t seen him yet not going the right way.

“He’s always trying to make a joke, so he brings such a fresh dynamic into the team and into Formula 1. Back home I have friends who are not necessarily fans of F1, but they are following now and they are impressed. It’s nice to see a young kid smiling and being so natural. It’s like he has always been here.”

That doesn’t mean Antonelli’s rise was preordained. The raw material was always there, but Mercedes – and Lagrue – helped mould it into a driver now on the brink of a first world championship. Most ominously for his rivals, he is only 19 and will get even better because he’s still a work in progress.