Alonso in champion form after Korea win
Alonso's superb victory in yet another thrilling race has turned the title race on its head - for the umpteenth time this year.
It moves the Spaniard, already a double world champion, into the lead for the first time since the Australian Grand Prix, the second race of the season, at the end of March.
It is a sign of just how close this incredible championship is that all five men who were in contention before this race remain so, even though Red Bull's Sebastian Vettel retired with an engine failure and Hamilton's team-mate Jenson Button could finish only 12th after a difficult race in his McLaren.
However, with only 50 points still available in the two remaining races, Button - 42 points behind Alonso - must effectively be counted out, as he admitted himself after what he described as "a pretty horrific day". Are you still in the championship, BBC F1 pit-lane reporter Lee McKenzie asked Button after the race. "Not really," he said.
Vettel, too, 25 points (one win) adrift, is in serious trouble, despite having what is undoubtedly the fastest car.
Both those two teams must surely now start to give serious thought to backing their leading driver over the other - as Ferrari have been doing since they asked Felipe Massa to hand the lead of the German Grand Prix to Alonso.
For Red Bull, in particular, it is an agonising situation.
Their emotional investment in Vettel has been clear for a very long time - and it was emphasised yet again when team principal Christian Horner was quoted saying before the Korean race that they were building the team around him for the future.
But unless some disaster befalls Alonso in Brazil or Abu Dhabi, it is difficult to see how Vettel can make up 25 points in two races on a man who has won four of the last seven grands prix, scoring more points than anyone, and whose last four results read: win, win, third, win.
Still, though, Horner told BBC Sport after the race that it was too early to start backing one driver over the other.
"As we saw in this race, different drivers were leading the championship at different points," Horner said.
"Fernando we gave a big gift today, and we need to look at that, but we have seen how quickly things can change.
"At the moment our strategy remains unchanged - this championship will not be over until the last lap in Abu Dhabi has been completed, and we will be pushing flat out until that time."
That is all well and good, but this is surely the point at which Horner - and team owner Dietrich Mateschitz - have to start asking themselves some hard questions and making some equally tough choices.
They have had by far the fastest car this season - a Red Bull has been on pole at 14 of the 17 races - and yet, for a variety of reasons, they find themselves with two races to go with neither driver leading the championship.
Alonso's advantage over Webber is not large - it is effectively the equivalent of a fourth place.
If, therefore, Webber won the two remaining races with Vettel second and Alonso third, Webber would win the championship. But if Vettel won them, with Webber second and Alonso third, then Alonso would be champion.
Complicating the issue is that, on the evidence of this season, the chances of Red Bull taking one-twos in the next two races are pretty slim.
There are two reasons to say that.
Firstly, Red Bull have proven again and again in 2010 that they cannot consistently deliver the results the performance of their car suggests they should.
Sometimes that has been down to the drivers, sometimes the team and sometimes things out of their control, such as the engine failure that hit Vettel in Korea. Whatever the reason, though, it keeps happening.
Secondly, it is far from clear they will, on pure performance, be able to dominate the last two races.
Of the two tracks, Abu Dhabi probably favours Red Bull more than Brazil. But neither of them are 'Red Bull tracks' in the fashion of, say, Suzuka, the Hungaroring, Silverstone or Barcelona. Both remaining events are difficult to predict.
Alonso, then, will remain a serious threat on pure competitiveness on the track and could well win in either Sao Paulo or Abu Dhabi. As Eddie Jordan pointed out in the F1 Forum, if you were minded to bet on anyone to win the championship, it would be the Ferrari number one.
Alonso drove another fantastic race in Korea. He was the only man anywhere near the Red Bulls on qualifying pace and in the race he buried an undeserved reputation for not being particularly good in the wet.
Although the Red Bull clearly has more downforce than the Ferrari, Alonso never let Vettel off the hook, pressuring him hard throughout the race.
Horner said Vettel had lost a "guaranteed race victory", but it did not look very guaranteed as the Ferrari closed right up to the gearbox of the Red Bull in the laps before its retirement.
Was Vettel managing the gap? It didn't look that way as he made a mistake and ran wide on lap 43, allowing Alonso to gain more than a second on him.
Was he already struggling from a lack of power that prefaced the failure? We may never know. But, until just before Vettel retired, the race still looked to me like a proper, flat-out fight between the German, Alonso and Hamilton.
What a battle it was. What a season it has been. And what a climax it promises to be.
Alonso might be favourite to win the title after what Martin Brundle described as "a champion's drive". But it is still all to play for. And after a year of so many twists and turns, you would be better off keeping your money in your pocket.