The sensational move will trigger a wave of questions and the ripple effect will cause a figurative tsunami through this season and the next.
Let’s consider a few of those big questions while the news is still white hot.
First, why is he doing it? Hamilton turned 39 on 7 January and, while Fernando Alonso is proof of how racing drivers can stay competitive well into their 40s, the seven-time champion knows he only has a finite time to make that number a record-breaking eight.
The decision is clearly a vote of no confidence in Mercedes-AMG giving Hamilton the car he needs to become a champion again.
There are no guarantees Ferrari can either, of course. But it seems he has weighed up his best chance – and stuck all his chips on red.
A switch to Red Bull? Impossible. Yes, it has the quickest car, but pairing Hamilton with Max Verstappen is a non-starter for all parties. There's too much history, too much tension, too much potential for severe headaches and angst to make that a realistic prospect.
No, it was always Mercedes – or what’s still the most famous racing team of them all.
What’s convinced him? Ferrari just lost out to Mercedes by three points last season to be the distant best-of-the-rest behind Red Bull last term but had a marginally better season.
Charles Leclerc’s five pole positions in the SF-23 highlighted how one-lap pace isn’t a problem, while Carlos Sainz Jr became the only driver not in a Red Bull to win a grand prix in 2023 when he triumphed in fine style in Singapore.
Meanwhile, Mercedes' form swung wildly from one weekend to the next, even as late as the penultimate race in Brazil, where the team expected to be competitive only to fall flat. F1 teams don’t like surprises, and Mercedes continued to have too many last season.
The team admitted early last year that sticking with its car concept introduced for the ground-effect rules reset in 2022 had been a mistake. It says it has learnt its lessons for this season when it will introduce an all-new approach.
The W15 has yet to turn a wheel – but Hamilton has lost his faith. He should know what’s coming, and clearly he’s unconvinced by the numbers.
With that in mind, perhaps he has reasoned that he has little to lose. Unless he has got it wrong and Mercedes has nailed its new design after all!
What about that point about turning his back on a manufacturer relationship that stretches all the way to his teens?
Hamilton has always been a Mercedes driver since his first season with McLaren in 2007. He could be a brand ambassador for life. But come on: think about it.
This multi-millionaire global sporting icon doesn’t need such a relationship. Finding a fruitful means of living when the wheels finally stop turning is hardly something he has to worry about. He lives in a different world to the one that Juan Manuel Fangio and Stirling Moss knew.
That old line was always irrelevant. A key aspect that will have drawn him to Ferrari is surely Frédéric Vasseur, who is beginning his second year in the biggest team principal job of the lot. Vasseur and Hamilton go way back, the Frenchman having run the teams with which the Brit won his Formula 3 and GP2 titles on the slippery climb to F1 20-odd years ago.
An irrepressible and likable character, Vasseur has made a strong start to leading Ferrari out of its latest era of underachievement. The project remains a work in progress – but the operational errors of previous years were fewer in number last year. Vasseur has been a unifying presence.
But from Ferrari’s side, why does it want a 39-year-old over the impressive 29-year-old Sainz? Because Hamilton proved in 2023 he still has the growling hunger to return to the top – and he drove as well as ever across the season. Give him the car and he will deliver.
Combined with Leclerc, Ferrari will likely have the strongest line-up on the grid next year – and Hamilton’s presence will galvanise and further motivate the team. He might well also aid Vasseur’s much-needed recruitment drive for fresh technical heads.
So what about this season? Hamilton signed a two-year deal extension with Mercedes just last August, but it seems the second of those had some sort of break option – which he has actioned a little more than a month before the start of the new campaign. For now, he remains a Mercedes driver. That’s going to be awkward.
We’ve seen such a scenario before. Alonso was announced as a McLaren driver ahead of the 2006 season but saw out his Renault deal before switching camps the following year. But how the dynamics can work this time around remains to be seen.
A Hamilton sabbatical, standing him down with immediate effect, would avoid a huge distraction in what is a crucial rebuilding year for the Mercedes F1 team. But at this late stage, who on earth could Toto Wolff sign to replace a seven-time champion?
The questions roll on. How will Leclerc react, given that he has just recommitted himself to Ferrari for an undefined long-term? Surely Vasseur told him this was possible. They also go back a long way.
What if Mercedes blows Ferrari away in 2024? That would sow a seed of doubt. And what if the Ferrari gamble does backfire in 2025 and Hamilton is forced again to dig deep for motivation? Will he have the energy and desire?
As we head towards a campaign in which the grid remains unchanged from one season to the next for the first time ever and one for which the fear is more of the same in terms of a Verstappen and Red Bull romp, the ‘Hamilton defects to Ferrari’ story will inject a dose of adrenaline into the F1 narrative that was much needed. The soap opera continues.
Last point for now: this is proof once again that no one should ever consider racing drivers as mere employees. You could say Hamilton owes his career to Mercedes, but the truth is the manufacturer has been blessed to have him. They have been good for each other, and anyway, loyalty is another red herring.
Racing drivers are always freelancers in spirit if not in contract. They will always seek out the best option to give them a chance to win, and if that means breaking old friendships and alliances, so be it.
Ayrton Senna, Alain Prost, Michael Schumacher, Alonso, even Fangio back in the 1950s: that’s what the big beasts do. It’s the law of the F1 jungle.