The British Grand Prix was a seismic moment in the 2021 Formula 1 title battle, featuring an incident that will become a defining part of the sport's history.
The two championship contenders collided, resulting in a high-speed crash for one of them and a brilliant if controversial victory by the other, and rancour and recriminations afterwards.
Max Verstappen called Lewis Hamilton "disrespectful" for celebrating while his combatant was in hospital. Hamilton, while expressing his concern for Verstappen, said he had nothing to apologise for and heavily implied that the Dutchman needs to learn not to be so aggressive. And Verstappen's team boss Christian Horner accused Hamilton of a "desperate move" and "an amateur mistake".
The fallout from all this will be felt for a long time.
It was an incident many had expected, because of the closeness of the racing between Hamilton and Verstappen this year, because Hamilton was never going to keep backing down in such situations in the way he has so far this year, and because it has happened so many times in the past.
Think of Ayrton Senna and Alain Prost, Michael Schumacher and Damon Hill, Hamilton and his former team-mate Nico Rosberg, among others.
The stakes are high in F1 at all times. A title battle raises them further. And one in which two different generations of driver are battling for supremacy, a young pretender trying to usurp the established number one, takes them into the stratosphere.
That was the scenario that led to the extreme bitterness that characterised Senna v Prost, and it is the same situation now. All that remains unclear for now is whether this one descends to the same depths as that did.
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The move that created this situation was a complex one to deconstruct.
The pair crashed at Copse corner, one of the fastest on the entire F1 calendar, after half a lap of hard, intense racing at the start of the race.
Hamilton started second, after Verstappen's victory in the new 'sprint' race on Saturday. The Mercedes had taken pole position for the sprint, but lost the lead after a poor start. In the grand prix, he made a better getaway than Verstappen, and was alongside into the first corner, Abbey, a curve just as fast as Copse.
Verstappen refused to concede, and held on around the outside, which becomes the inside for the next corner. Through the complex of slow corners at Turn Three and Four they tussled, Hamilton positioning himself for the best exit on to the Wellington Straight.
He got a run on Verstappen and was actually ahead on the outside as they turned into Brooklands, but had to give way as he slid a little wide.
Now, he went for a better exit from Turn Seven, Luffield, which funnels out on to the old pit straight that leads to Copse. Up until then, the battle on Sunday had been very similar to the one they had had a little less than 24 hours before - if even more intense. But this is where it changed.
"I got a great tow down to Turn Nine," Hamilton said. "Yesterday, I went down the left and really regretted not going for the gap that was on the right-hand side.
"So I dummied him, moved to the left and then moved to the right for that gap. I was pretty far alongside him but I could see he wasn't going to back out. Then we went into the corner and we collided."
Hamilton had the majority of his car alongside Verstappen's as they turned in, but the Red Bull driver had squeezed him tight to the inside before moving back towards the left, so Hamilton was approaching Copse at a shallow angle.
Because of this, he had to back off a little, knowing that if he did not, the two would collide. But even so, he was wide of the apex of the corner.
Verstappen turned in initially, then moved a little left when he saw Hamilton on his inside, before turning right again. They touched, the fact it was left front of Hamilton's Mercedes to right rear of Verstappen's Red Bull belying the fact of how far alongside Hamilton had been on turn in.
Horner was furious. "He ran wide into Max, with too much speed," he said. "That move was never on."
Horner said he believed the occasion had got to Hamilton - losing the sprint race, the huge partisan crowd supporting him. And - although Horner did not mention it - of course the fact that Verstappen was 33 points ahead in the championship before the race.
"I think he was wound up after yesterday's result," Horner said. "You could see that yesterday, the crowd. He was fully motivated and made a massive misjudgement.
"He got a penalty for it, but it's fairly meaningless. It was his only opportunity and he knew had Max come through that corner he might not have seen him again for the afternoon. For me, it was a desperate move that thankfully didn't have worse consequences than a written-off car and badly bruised driver."
The stewards adjudged Hamilton to be "predominantly at fault" and handed the Mercedes driver a 10-second penalty, from which he recovered to win the British Grand Prix, extending his record at Silverstone to eight victories.
But other drivers did not agree it was an incident worthy of censure.
Ferrari's Charles Leclerc was right behind the collision and inherited the lead after it, and lost what would have been his first victory of the year when Hamilton passed him for the win with two laps to go. He said: "It is a racing incident. It is quite difficult to put the blame on one or the other.
"There was space on the inside. Maybe Lewis was not completely at the apex but it is also true Max was quite aggressive on the outside. Things happen. The most important today is Max is unharmed and is fine."
And Fernando Alonso, a two-time world champion, who has passed people around the outside of Copse a number of times in his career - including in the sprint race on Saturday - said: "Lewis had more than half a car alongside Max, so in a way Lewis could not disappear from that inside line. You can't vanish. So it was an unfortunate moment but nothing intentional and nothing that any of the two drivers did wrong."
What do the rules say?
Mercedes boss Toto Wolff made reference after the race to the stewards' overtaking guidelines, which he said allowed Hamilton to make the move.
These are not distributed publicly, but they have been seen by BBC Sport. They contain images of two cars on entry to a corner, and illustrate when a driver trying to pass has the right to claim it.
They state that if the driver on the inside has "a significant overlap" then "the corner is yours provided you make the corner cleanly". In the image in this illustration, the overtaking car is not even as far alongside as Hamilton was as they turned into Copse on Sunday.
As with so many F1 rules, there is ambiguity there. Hamilton did have a significant overlap, so was entitled to think he could claim the corner and that Verstappen should back off enough to give him the room for both to make it through.
But what does "make the corner cleanly" mean? Verstappen - who has spoken since only in a couple of brief messages on social media - would doubtless argue that Hamilton did anything but. After all, they collided. Hamilton might well counter that he did make it cleanly - even after they had contact.
How will it affect the dynamic of the fight?
What happens next is as interesting as the incident itself. Deliberately or otherwise, Hamilton has sent a powerful message to Verstappen.
This was the first crash between the two this year, but it was not the first incident in which Verstappen has used aggression to try to keep or take the lead.
In the races at Imola, Portimao and Barcelona - three of the first four this season - Verstappen was very forceful in defence or attack, and each time Hamilton backed off to avoid a collision.
This time he did not.
He said: "There is rarely an incident that is 100% someone's fault. It is always a mixture, because there's two people or more. There are things we can both learn.
"Max is probably one of the most aggressive drivers here, just in my opinion. He does a great job, of course, but I think we have to find the best balance we can on track with space and respect between one another so we can have good races without colliding.
"When I was younger, I was probably as aggressive… well, maybe not as aggressive as Max, but pretty aggressive as a youngster. But I am a lot older now and I know it's a marathon not a sprint, and I have a better view of how to approach my racing.
"He has been very aggressive and most of the times I have had to concede and just avoid the incident and live to fight on later in the race.
"As you saw yesterday, once he is out in clear air, they are too fast. So, when an opportunity comes, I've got to try and take it. That's what we're out there doing. I'm racing.
"I got a great exit out of Turn Seven and was really happy with the dummy. I was able to go to the left and then go to the inside and get up that gap. Fortunately, he wasn't able to close it. But unfortunately the aggression stays from his side and we collided. It's unfortunate but it's a racing incident, these things happen."
Later in the race, the move with which Hamilton won the race was almost a carbon copy. Again, he went for the inside, this time of Leclerc. There were two main differences - Hamilton was on the racing line, rather than slightly wide of it; and Leclerc gave him more space.
Hamilton said: "He was very respectful on leaving a gap. I got somewhere alongside him. He knew I was there but he stayed committed and did a wider line and he nearly kept it.
"I backed out at one point just to make sure that we didn't come together but I think it was just a really nice balance and I think that's really how the racing should go.
"In a perfect world, that's what would have happened in the first attempt. But different time, different place, different driver."
Everyone will have their own opinion of the incident, but among the many consequences is that the championship battle, from looking like Verstappen was beginning to run away with it, is now close again. Verstappen remains favourite, but his lead is down to eight points.
"It's been such a hard year," Hamilton said. "One I've thoroughly enjoyed. I've loved this battle but it is an emotional rollercoaster, as it always is within a championship.
"I really enjoyed those first four races where it was close, as it was this weekend. Then we saw them take that step ahead and I would say we've definitely made some mistakes as a team but just also lost a bit of performance.
"So to see an upgrade [to the car] come back and us get back in the fight and be relatively close and to even be able to qualify ahead was really, really amazing.
"Did I think that we would be back in the title fight? Jeez, I don't know. I prayed and hoped for it but I thought that it would be a long slog to try and regain any of the points. But we're now closer; he's still got quite a few points ahead but the race is on."
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