Great final corners make history, every track should have one. A chicane, or a wide, tight final turn which allows riders to attempt a desperate last-gasp plunge up the inside, or for the exceptionally brave, round the outside, for the win. The truly great corners have just enough options after the turn for the attacking rider to make a mistake and let the rider he just passed retake the lead.

Assen has such a final corner. And not just a great final corner, but also a great sequence of corners which lead up to it, allowing riders to both plan ahead and to react to the unexpected. On Saturday, Assen's GT Chicane, and the complex from De Bult all the way to the exit of Ramshoek, delivered spectacular and exhilarating racing. It also delivered a moment which will go down in the annals of MotoGP history, and be debated for years to come. It might even prove to be the decisive moment in the 2015 championship.

The names of the protagonists should come as no surprise: Valentino Rossi led into the final corner, with Marc Márquez in hot pursuit. What happened next depends on whose version of events you wish to believe, as the participants differ in their perceptions. Rossi says he turned in to the first part of the chicane in front, got bumped wide by Márquez, and had no choice but to gas it across the gravel to avoid crashing. Márquez says he had the inside line in the corner, Rossi cut him off, then cut the corner on purpose to take the win. Which version is the truth? We'll come to that later, but to understand what happened we have to go back to the beginning of the race.

Rossi's success has its roots in Barcelona, when he and his team found an improvement on Saturday morning which allowed him to be competitive in Catalonia. The new set up worked even better with the new chassis at Assen, and Rossi was on the pace from the start. Qualifying on pole for only the third time in five years put him in a good position to get away on the start, and he capitalized on his pole as soon as the lights went out. Aleix Espargaro slotted into second, managing to hold on to his position off the line thanks to the short run to the first corner, and Marc Márquez followed in third. At the Strubben hairpin, Márquez cut underneath Espargaro and hammered on the gas, latching onto the tail of Rossi, the pair quickly disappearing into the distance.

Jorge Lorenzo followed, charging through the field with clinical precision from eighth on the grid. By the time he was halfway round the track, he was up into third, sliding inside the other Espargaro brother Pol at Mandeveen. Lorenzo tried to catch the leading pair, but their pace was just too hot to follow, and he had to let them go. He was never threatened for third, and rode home to a lonely podium.

At the front, Rossi had taken off like a scalded cat. Márquez stalked, his Honda RC213V looking better than it has all year. The rear slides and fishtailing on corner entry were much reduced, and it looked like Márquez had control once again. Even as the tires began to wear, Márquez kept control, the bike never sliding out of control like it had at Barcelona and Mugello. Though the bike was still making some rather acrobatic shapes, Márquez was still hitting every apex he aimed at precisely. Was his bike better? "I want to be careful, because it's only this weekend," he answered at the press conference. "But what I feel is that I enjoy again on the bike. We still need to improve the slide on entry, especially in the last part of the race." He was able to follow the pace set by Rossi comfortably, and be in good shape to attack later in the race.

And what a pace it was. Every one of Rossi's flying laps was under the existing race record, the only exceptions coming when swapping the lead with Márquez. The same was true for the Repsol Honda man, only going slower than the record when he was attacking the Movistar Yamaha rider. Márquez watched Rossi carefully for the first 19 laps, then pounced when Rossi ran over the astroturf on the outside of the final chicane and lost drive onto the straight. He was through into Turn 1, and it was Rossi's turn to stalk.

The Italian clearly still had a trick or two up his sleeve, and with three laps to go, he lined up a move through the inside of Mandeveen, holding the tight line to take back the lead. Márquez tried to come back at Duikersloot, but found the Yamaha blocking his way. It was a classic Yamaha move, described by Bradley Smith a day earlier as "arrive on the apex and say 'hello!'"

Rossi knew he had to try to go for the kill and put in his fastest lap of the race. He opened the gap to just over half a second, but now Márquez knew it was time to respond. On the final lap, Márquez inched closer corner by corner, until he was close enough at the Ramshoek to try that last gasp dive up the inside of the GT chicane which Assen is famous for. It was, he said in the press conference, the move he had been practicing all weekend, ready for just such a moment as this. "My plan was to go in on the first corner and then close the second one. Because then the other rider don’t have the space and you have already the position."

Márquez attempted to dive up the inside of Rossi, but never quite got his front wheel ahead of the Yamaha's. He made it about as far as the radiator of the M1, but that was not far enough to have secured the position. Rossi, knowing Márquez was near but, he said, able to see only his tire, closed the door on the Honda, as he had every right to do as the leader. But Márquez was in too deep, and hit the inside of Rossi's fairing, bumping Rossi off line and making his own RC213V wobble. Rossi reacted instantly, picking his bike up, gassing it up and pointing it straight through the gravel at the finish line. Márquez regained control of his Honda, cut across the inside of the astroturf, and crossed the line furious at not having won.

After the race, Rossi said he entered the corner and was on the line, and only cut across the gravel because he was forced to by Márquez. Márquez saw it differently, claiming he had the right to the corner as he held the inside line, and suggesting that Rossi should have the win taken away as he had cut the corner. Honda immediately rushed to Race Control to lodge a complaint, but Race Direction had very quickly come to the conclusion that this was a racing incident, that both parties had cut the final corner, and that the result would stand. Honda accepted the decision, and after the post-race conference was finished, both Rossi and Márquez were called to Race Direction, and shown the video from the many different angles which Race Direction have, in addition to the standard broadcast feed.

A group of journalists spoke to Race Director Mike Webb after the race, and this is what he told us. "It obviously needed review, so as soon as we saw it, and because it’s the last lap we can then pay our attention to it. So lots of video reviews, lots of discussion. I have to say the end result, race incident, was clear cut. It wasn’t we're not sure or whatever. It was clear cut. The basis of that was that during the entire last chicane maneuver Valentino was always in front. We have a really good helicopter shot that he's always in front and is therefore entitled to his line. He was entering the turn and doing a normal line as if he was going to go through the turn. Marc made a pass on the inside, which he's entitled to do. It's the last lap of a GP, have a pass. During the pass he first of all critically never got in front of Valentino. The helicopter showed us very clear, Valentino’s always in front. Marc did make contact with Valentino."

Was it Márquez hitting Rossi, or Rossi hitting Márquez? "Very clearly Marc made contact with Valentino. The helicopter shot shows us who’s in front. The frontal shot which was not the live shot, but another shot from front on, shows the gap between the riders and which trajectory they’re coming on. Valentino’s on pretty much the classic line. Marc’s doing a pass up the inside as you would, and arrives and contacts Valentino. Valentino at that point decides he has to stand up. He said, I’m on the limit. He’s going as fast as he can into the turn, gets contact from the inside, has no option but to stand up. So he goes across the gravel. Marc also leaves the track, goes across the artificial grass. So from the rules point of view both riders left the track. They entered the turn and through the turn and exited the turn in the same relative positions, as in first and second. At no point did they change positions. So from that point of view no advantage was taken. Clearly because Valentino cut a lot more of the corner there was a time advantage taken but in this instance it’s immaterial. We’re not waiting for the next lap to see who’s got an advantage. It was the person in front stayed in front. The person in second stayed second. They both left the track and they both regained the track. End of story. The critical point is that I believe both riders entered the turn intending to make the turn. No one was intending to cross the gravel. No one was intending to knock the other rider off. But what happened was contact and then a rider left the track, both riders left the track. So in the end pretty simple. Racing incident, no advantage was taken."

Webb said that Márquez was entitled to try to make the pass in the final corner. "Marc had a legitimate attempt to make a pass. I believe he did not intend to make contact with Valentino, but he did." The goal of Race Direction is to ensure that the racing is safe, but that it remains racing, and that riders are allowed to attempt to win the race on the last lap by taking more risk than they might on any other lap.

Was Márquez' pass legitimate? Watching practice and warm up, you can indeed see him taking that same line through the corner a number of times. The minor complication being that when he did it during practice, there wasn't another rider there to ruin the line. But in that respect, it was a trademark Márquez move, planning his own line through the corner without overly concerning himself for the plight of the riders he is passing. With any other rider, he might have got away with it, though in that case, Race Direction may have taken a different view. "There are other incidents with Marc in the past, with other riders in all the classes, where our opinion is that the pass had no chance of coming off, that it was deliberate contact or something like that in which case there’d be a penalty. In this case it’s a fair attempt at a pass on the last corner of the last lap that resulted in some contact. It wasn’t particularly strong contact, but it resulted in contact. Luckily the end result was that the positions stayed the same. If one or both had crashed as a result of that we’d have to look at the incident in the light of that, but luckily they didn’t," was Mike Webb's view of the incident.

The problem for Marc Márquez was that he did not try that move on just any old rider, he tried it on Valentino Rossi. Rossi has been racing at Assen for over twenty years, starting in the European championship and then all throughout his Grand Prix career. He has seen a lot of racing here, and has the experience to cover all eventualities. He saw his former teammate Colin Edwards have trouble in this corner in 2006, and Nicky Hayden steal the win taking almost exactly the same line. Rossi must have been all too aware of the options he had at that corner, and instinctively picked the right one. To put that into perspective, Marc Márquez wasn't even racing in Grand Prix in 2006.

Perhaps Rossi even entered the corner already knowing exactly what his options were in case of contact. Bradley Smith had an illuminating take on the entire incident. "Valentino played the circumstance perfectly to his advantage," Smith said. "He made sure Marc hit him so then he had to go across the gravel and no one can say anything. That’s finally what it is. There’s however many years of experience right there. He closed the door. He timed it perfectly so that when Marc went for it he hit him and knocked him off the track. Then you can’t say anything because Valentino said 'yeah, I’m going to make the corner'. Whether he could or not is up to interpretation but he can say 'the reason why I went straight on is because Marc hit me and I had the lead going into the chicane so I didn’t actually technically gain an advantage so I should actually win the race'."

Did Rossi really mean for Márquez to hit him? That seems unlikely, but you have to believe he factored it in to his decision making. In Rossi, Márquez may have finally met his match, the physical intimidation which has worked on so many other riders simply will not wash at this level. Jorge Lorenzo showed in Sepang 2013 that he would not be intimidated by Márquez, and was happy to give as good as he got from Márquez. Now Rossi is taking that a step further, planning to absorb and deflect Márquez' physical style, and turn it against him.

There have been many complaints in the past that Márquez has no regard for other riders, and that he charges in with no regard for their safety, and no respect for their rights to be on track. Jorge Lorenzo believes a one-race ban is the only thing that will make Márquez alter his ways, just as it worked with Lorenzo after Motegi 2005. But Rossi's medicine could perhaps be even more effective. Banning Márquez for one race would be painful, but using his own tactics against him to steal victory from him is a very special kind of torture. The next time Márquez ponders trying to muscle Rossi out of the way in a bid for victory, he may pause for thought, and look back to Assen 2015. He may realize that his only real hope of beating the Italian veteran is by making sure his passes will stick. That means not resorting to physical bullying, but actually ensuring he gets ahead and stays ahead.

That this had been a painful lesson was all too clear at the post-race press conference. It was a deeply fractious affair, the light-hearted banter and fellowship between Rossi and Márquez notably absent. There was plenty of joking – the best of it coming from Jorge Lorenzo, surprisingly, the Spaniard given the space to display his wit, without the need to get defensive about his own performance – but the two protagonists were sticking resolutely to their guns. Rossi, as the winner, had the lightest load to bear, history and the results sheet on his side. Márquez was more querulous, stating repeatedly that he had done nothing wrong. "What I did, I think, was the perfect last chicane because I go in and I stop the bike to be on the correct line to cross later the space for Valentino, for the second chicane," Márquez said. Then later, "I did the perfect chicane with what I planned yesterday." Later still, "What I know is that I did the correct [thing] because I didn’t go outside the track. What I already say, I think I did the perfect last lap, perfect last corner. I prepared like this. But when I stopped the bike completely and I had already the place there inside then we had the contact but we already know that in that chicane it’s really tight. I know that I did the correct [thing]."

Rossi's reply was simple: "Maybe it's better that we see another time the images." They did, after the press conference, up in Race Control with members of Race Direction. BSB race director Stuart Higgs posted a photo of the two watching the video, and the faces of the two riders spoke for themselves. Márquez did find a way to vent his frustration with humor. When asked what he had learned from Rossi at Assen, he shot back "some motocross, nothing more."

The most ironic moment in the press conference came when Márquez was asked what he would have done had he been in Rossi's position. "You never know, but after this experience, I know what I need to do," he said darkly. The words were almost identical to those used by Lorenzo at Jerez in 2013, when Márquez bumped him in the final corner to take second. "Let's see what happens in the future," Lorenzo had said then.

Mike Webb was left unimpressed by Márquez' veiled threat. "I’ve been through this a lot of times where riders have felt that they’ve been done wrong and their reaction in many, many cases is if that’s allowed then I’ll carry on doing it. Almost like a threat. Sorry, but I’ve heard it too many times. It’s not even worth comment, really." In the heat of the moment, riders say a lot of things, but very rarely do the actually follow through on them.

If there was a winner from the press conference, it was Jorge Lorenzo. Invited to pick sides, Lorenzo skillfully avoided the trap laid for him, and left the audience laughing. He managed to get subtle digs in at both riders, as well as give the journalist who asked him the question enough rope with which to string himself up. Later, when asked if the battle between Rossi and Márquez could help him in the championship, he quipped, "if they had crashed today for sure it would help me a lot..." After a race where Lorenzo had been unable to follow the two leaders, he managed to regain the momentum in the press conference. It was well played, and an opportunity well taken.

Does the incident at Assen mean that the relationship between Rossi and Márquez will change? They both denied it, of course, but inevitably it will. With the championship firmly in sight, Rossi's attitude towards his rivals is hardening again, his demeanor changing subtly to put a little more distance between himself and the rest. When Márquez first came into the class, and Rossi was struggling to get his head round the Yamaha again after his time at Ducati, Rossi may have viewed the Spanish youngster as his heir apparent, and treated him with a certain fondness. That continued into last year, even when the two were battling for victory. Now, though Rossi remains friendly and smiling, laughing at Márquez' jokes, the banter between the two has acquired a certain edge. It is spikier, more barbed, though there is still great respect.

Does this herald a return of the Rossi mind games? I have never really been convinced that his tactics were deliberate, or even especially successful. Rossi's greatest asset in his battles with rivals was always his riding on the track, rather than anything he might have said off it. The Italian does appear to be putting a little distance between himself and Márquez, as he starts to believe in his championship chances, and sees that Márquez could ruin it for him, not as a title rival, but by stealing points in the races. Valentino Rossi is always seen as a joker, a clown, and a big friendly bundle of fun. He may well be all those things, but he certainly isn't when it comes to motorcycle racing. Racing is serious business, winning even more so.

Will Assen 2015 be a Laguna Seca 2008 moment? It can't really be, as the man beat at Assen had no hope of winning the championship. In 2008, Rossi beat Casey Stoner in a straight fight, one of the most bloodcurdling and exhilarating duels in the history of racing. With victory there, he swung the momentum of the title race away from Stoner and towards himself. At Assen, Rossi went up against Marc Márquez and beat him decisively, putting him in his place. In doing so, he extended his lead over Jorge Lorenzo, taking it out to ten points. The fact that it was Márquez who was forced to finish second will have no bearing on the championship, other than it slightly decreases Márquez' chances of coming third.

The real rival Rossi faces is his Movistar Yamaha teammate. He may have beaten Lorenzo convincingly at Assen, but he did not deal him a psychological blow as he did so. Lorenzo was slower, because the lack of edge feel on the tires made it hard for him to follow Rossi's pace. That was merely returning the favor for what Lorenzo had done to Rossi for the past four races. Assen may yet prove to be a pivotal race in the championship, but this was not the race where Rossi broke the spirit of his teammate. That battle is yet to come, but come it surely will.

To spend nearly four thousand words on just a single pass is to do a massive injustice to the remainder of the weekend. There was so much to talk about at Assen that it will not fit into a single story. The tale of the Suzuki, Andrea Iannone's mature and measured ride, Andrea Dovizioso's broken rear seat unit, the battle for fifth, Pedrosa's problem with the brakes on his Honda, a new basis for the MotoGP class, Johann Zarco's increasing grip in Moto2, and last but not least, a scintillating Moto3 race which saw Danny Kent increase his championship lead yet again. All that will have to wait until another day. More on Assen tomorrow.