An even bigger collision deeper in the pack threatened to bring the safety car back into play, but the marshals were able to clear the wreck of Wurz's Williams - which had gone out of control under braking and clattered into Massa's Ferrari - before the pack returned, allowing Hamilton to continue unhindered.
Massa, meanwhile, saw his race go from bad to worse as, despite surviving the clout from Wurz, he was summoned for a drive-thru' penalty, punishment for retaking his position after spinning under the safety car. Clearly fired up, the Brazilian skated off at turn one, again rejoining undamaged, but he wasn't quite as hot under the collar as local favourite Takuma Sato, who pitted for a new front wing but had his car catch light as the Super Aguri team carried out a routine fuel and tyre stop. Sato appeared unaware of the peril as he raced out of the pit, but the increasingly heavy rain provided suitable extinguishant and the Japanese was able to continue.
The leaders, split by just over two seconds, were lapping in the 1min 28s range by the time they were finally forced to pit for fuel and tyres, Alonso stopping first. The eleven-second stationary time confirmed that McLaren was now able to contemplate the switch to a single-stop strategy, but the world champion's exit proved slightly mistimed as he rejoined in the midst of the battle for fourth involving Giancarlo Fisichella, Heikki Kovalainen, Robert Kubica and David Coulthard, miring the Spaniard in seventh.
Hamilton stopped next time around and, having pressed on once Alonso disappeared from his mirrors, got off a lot lighter as he pulled back into line ahead
of the Renaults. The Briton was, however, only third on the road, having been passed by the unlikely duo of Sebastian Vettel and Mark Webber while he was serviced.
Vettel peeled off for his lone stop approaching half-distance on lap 32, allowing Webber to hit the front and rejoining not far behind Alonso, who had had a moment in the thick of battle and dropped to eighth behind Coulthard. When the recovering Heidfeld then passed Alonso on the road, the Spaniard fell into Vettel's clutches, but the pair got a little too close for comfort two laps later, when Toro Rosso appeared to tag McLaren, spinning Alonso around and allowing Raikkonen to move ahead of the Spaniard.
While the world champion's cause appeared to have taken a major hit, Hamilton was not having things all his own way and, if anything, received an even heftier clout from Kubica as the Pole sensed a chance to pass the now more heavily-fuelled Briton. Knocked into a spin, Hamilton ceded spots to both Kovalainen and his attacker - although Kubica would later receive a drive-thru' for his part in the altercation - and then saw Fisichella and Coulthard slip by as he attempted to regain his composure. However, all four cars ahead of him still had to stop, leaving the Mclaren safe in the knowledge that he should retake the lead once the various strategies played out.
It took until lap 41 for the order to return to something approaching normality, with Fisichella the last to relinquish the lead and Kubica serving his penalty, but the race - and the championship - took an even more decisive twist just one tour later.
Still with the serviced Webber and Vettel between himself and his team-mate, Alonso had been pressing on as the conditions worsened, although his right sidepod was clearly carrying the scars of contact with the young German. On lap 42, however, the pace became too much as the world champion lost it exiting turn five at around 140mph, slamming into the wall before coming to rest in the middle of the track. Fortunately, the rest of the field missed the wheel-less McLaren, but Alonso's day - and possibly his championship hopes - were done.
With debris scattered over a wide area, the safety car was called for and the field again packed up behind Hamilton. Remarkably, Alonso had been only the second retirement of the race, joining Wurz, suggesting that the stewards' decision to go racing had been the right one - even if the drivers still largely disagreed. The casualty list was about to get bigger, however, starting while the pack was still running at controlled speed.
Some two laps before the decision was taken to resume, Webber's car speared out of second place and into the wall. At first glance it appeared that the Australian - who had been running faster than Hamilton at the time of Alonso's off - had lost it while warming his tyres, but subsequent replays showed that Vettel had been at fault, slamming into the back of the Red Bull Racing entry as both attempted to keep temperatures up. The German accepted the blame, but hinted that he had been caught out by Hamilton's extreme accelerating and braking behind the safety car rather than by his own lack of awareness of Webber's position.