Lewis Hamilton celebrated his third victory of the season on a day Jenson Button's hopes of back-to-back world championships suffered "a massive blow."
Hamilton took the chequered flag after a typically chaotic Belgian Grand Prix in which three of his main rivals all failed to score a point.
In finishing 1.5 seconds ahead of Mark Webber as the race ended in the wet, Hamilton has leapfrogged the Red Bull racer at the top of the standings, with his cushion now a marginal three points.
It was Webber's team-mate Sebastian Vettel who was again the major talking point during and after the event, notably for causing yet another accident, this one accounting for Button.
With Hamilton and Button running one-two, the latter came under attack from Vettel on lap 17, only for the German to lose control of his car under braking into the bus stop chicane.
As he fought for control, Vettel skewed one way and then the other before spearing into the sidepod on the left-hand side of Button's car, bursting the radiator and forcing him into retirement.
It was an error scathingly criticised by McLaren team principal Martin Whitmarsh as "not what you would expect to see in Formula One, more reminiscent of junior formulae."
Vettel collected a drive-through penalty, his second in successive races, before then suffering a puncture later on after running over the front wing of Force India's Vitantonio Liuzzi, finishing 15th.
It was also a blank day for Fernando Alonso, who previously had revived his title hopes in the last two races by finishing first and second.
But after surviving being run into by Williams' Rubens Barrichello whose historic 300th grands prix ended before the first lap, Alonso then broke the front-right suspension of his Ferrari after spinning into a barrier in the wet on lap 38.
With such incidents and casualties, it was a good day for Hamilton and Webber, who suffered a clutch issue off the line as he slipped from pole to seventh before recovering to finish as runner-up.
The victory was particularly significant for Hamilton after being demoted from first to third in 2008 via a penalty after the race.
Over the radio Hamilton said of his win that "it feels like the first time," and his exuberant post-race celebrations certainly underlined his depth of feeling.
"I think you can probably see by my reaction just how happy I am," said a beaming Hamilton, who narrowly avoided a barrier after going wide into the gravel as the rain came 10 laps from home.
"I love racing. It is in my blood, and I missed it so much in the break.
"We came here surprisingly to see we were very competitive, if not a little faster than the others.
"To then put that into a win in the changeable conditions was very tough, but it's one of those I can tick off now and say I have won.
"And I get to keep this one which is great, so I'm very, very happy and the team did a great job. What the whole team works for is that win.
"Obviously, I'm sorry to hear what happened to Jenson. It was very unfortunate for him and for us as a team.
"He was doing a fantastic job to get up to second and those points were very, very valuable."
They were precious to Button, who now finds himself 35 points off Hamilton, and who was naturally left cursing Vettel.
"I don't know what happened with Sebastian. I just felt a big bang in the sidepod, knocking out the radiator, and I completely lost drive," said Button.
"It was a very strange incident. I don't know what he was doing.
"He ended up in the side of my car and that was it, game over. It's a massive blow for the championship that hurts quite a bit.
"I'm now 35 points behind the lead, which is a long way and it puts me on the back foot. I'm pretty down."
That was naturally in contrast to an upbeat Webber, despite losing his lead as he said: "I'm happy with second in the end.
"The order is slightly the wrong way round for me, but it's a good day for the team, and Lewis deserved the win. He did a good job."
Renault's Robert Kubica was third, followed by Felipe Massa in his Ferrari, Force India's Adrian Sutil, and then the Mercedes duo of Nico Rosberg and Michael Schumacher, who had started 21st.
Sauber's Kamui Kobayashi was eighth, Renault's Vitaly Petrov ninth, with Liuzzi promoted to 10th after Toro Rosso's Jaime Alguersuari had 20 seconds added to his time post race for cutting a corner and gaining an advantage.