Schumacher of old returns to haunt Hamilton
Since Michael Schumacher returned to Formula 1 at the beginning of last season, he has not provided many glimpses of the man who dominated Formula 1 for so long - but that all changed at the Italian Grand Prix.
It is still not clear whether the German legend has the speed he had in his first career, despite two impressive drives in the last race in Belgium and now on Sunday in Monza.
But it was blatantly obvious in Italy that he is as willing as ever to push the boundaries of acceptable behaviour up to and beyond their limits.
Schumacher's driving in defending his position from Lewis Hamilton will split opinions - as BBC Sport's own experts proved.
"In sporting etiquette between racing drivers," David Coulthard said, "that was right on the line and he had one foot over it. He gave Lewis the chop."
But while Coulthard went on to add that he did not feel Schumacher deserved a penalty for his behaviour, chief analyst Eddie Jordan disagreed: "You cannot move twice. It's certainly questionable. If I was a judge I would have to reprimand him."
Schumacher's defence of the position over 21 enthralling - and occasionally heart-stopping - laps was certainly robust.
But there were two incidents in particular for which many will argue he was lucky to get away without a penalty.
The first was on lap 16, when Hamilton dived down the inside of Curva Grande - taken flat out at 190mph - and Schumacher pushed him on to the grass.
The second was four laps later, when Schumacher appeared to change his trajectory twice while defending from Hamilton out of the second chicane and into the first Lesmo corner.
Article 20.2 of sporting regulations says: "Manoeuvres liable to hinder other drivers, such as more than one change of direction to defend a position, deliberate crowding of a car beyond the edge of the track or any other abnormal change of direction, are not permitted."
It should be no surprise that Schumacher is prepared to drive like this - after all, he did it so much in his first career that his dubious tactics are remembered just as strongly as his results, which takes some doing when you have won nearly twice as many races as anyone else in F1 history.
What is perhaps more surprising is that he was not punished - particularly for the 'two moves' incident. Although this looked less dramatic, it was probably the one that further exceeded the boundaries of acceptability.
The blocking move into Curva Grande was, as one veteran F1 observer put it on Sunday evening, "a bit naughty but entirely predictable" - and Hamilton was anyway a bit optimistic in trying to go down the inside there from as far back as he was.
Race director Charlie Whiting warned Mercedes about Schumacher's driving - and team principal Ross Brawn was fully aware of how close they were to being penalised. He went repeatedly on to the radio to warn Schumacher to give Hamilton enough room.
Back in Malaysia in April, Hamilton was given a 20-second penalty after the race for changing his line twice while defending his position from Fernando Alonso. Many will look at Schumacher's behaviour in Monza and conclude it was at least as bad, if not significantly worse.
Hamilton himself was clearly unimpressed. "I thought you were only allowed one move!" he said in exasperation over his radio.
After the race, though, he kept his counsel in public. As he had made it clear he wanted to stay out of trouble to try to end the tumultuous run of events that have derailed his season, that is perhaps not a surprise. It remains to be seen whether it stays that way.
Ironically, it was the first of those two incidents that led to Schumacher losing what at the time was third place, a position he found himself in after his customary superb start, and then taking advantage of Hamilton being caught napping at the re-start after the safety car period that was prompted by a first-corner crash involving backmarkers.
In backing off after being forced onto the grass at Curva Grande, Hamilton was overtaken by team-mate Jenson Button, who used his momentum to close rapidly on Schumacher and pass him in a brilliantly audacious move around the outside into Ascari.
Button said his own move on Schumacher was one of the bravest he has ever pulled, but another earlier in the race surely surpassed it - when race-winner Sebastian Vettel passed Alonso for the lead around the outside of the Curva Grande and into the second chicane.
Alonso edged Vettel far enough to the left for the Red Bull to have its left-hand wheels on the grass while flat out in top gear. But Vettel kept his foot hard down, controlled what must have felt like a scary wobble, and nailed the Ferrari down the inside into the chicane.
It puts to bed any unfounded criticisms that Vettel cannot win from behind - and the world champion elect was still a little wide-eyed about it after the race.
"I was on the grass there," he said to Alonso with a smile as they waited to go out on to the podium. "Yeah," the Ferrari driver responded.
It was a heart-in-the-mouth moment, certainly, but was this as bad as Schumacher's chop on Hamilton into the same corner a few laps later?
Schumacher appeared to turn in early on Hamilton and gave him no room at all, and the McLaren driver had no choice but to take to the grass with at least half of his car. Vettel, by contrast, had the option to back out of the move, but chose not to.
This was almost certainly because - as with team-mate Mark Webber's pass of Alonso into Eau Rouge at the last race in Belgium - he knew Alonso would be hard, but could trust him to leave him just enough survival space.
It was mighty close. "Very hard but fair," was Vettel's post-race verdict
What was particularly impressive about Vettel's decision to commit was that he did not need to - as he himself said, he could easily have waited and got him in one of the zones where he could use his DRS overtaking aid that lap or the next.
Vettel has such a huge championship lead that he does not need to take any risks - and yet his hunger for victories, to stamp his absolute authority on this season that surrendered to him months ago, remains as intense as ever.
This was his eighth win of the year and one of the most impressive, and suitably it brought him to the brink of his second title.
Vettel will be crowned the youngest double champion in history - taking the honour from Alonso, ironically enough - in Singapore if he wins and Alonso does not finish third and Button or Mark Webber do not finish second.
On current form, that is entirely possible, and even if he doesn't do it there, Vettel will certainly tie it up sooner rather than later.
At the age of 24, he has 18 wins to his credit, a second title in the bag, and 25 pole positions. Schumacher's records - 91 wins, 65 poles, seven titles, which seemed unbeatable when he set them - look within reach, unless the other teams can do something about Red Bull's superiority. And perhaps even if they do.
Vettel's remarkable progress prompted superlatives from Coulthard after the race. "Are we witnessing one of the true greats - one of the legends of the sport. It's always difficult to judge when it's so early in someone's career but his results are remarkable."
To truly judge Vettel, he needs to go up against another great - Hamilton or Alonso or perhaps, on current form, Button - in an equal car. But there can no longer be any doubts that he is right up there.