All this early weather-related chaos had comprehensively scrambled the field behind the leaders, with Hamilton and Alonso ahead of Vettel whose recovery amid the spins and pit stops had already put him into back up fifth ahead of Kobayashi, Webber, Nico Rosberg, Paul Di Resta and Daniel Ricciardo. Not that it was looking like settling down anytime soon: with the rain now easing, the drivers were burning through their intermediates at a ferocious rate and the teams were soon forced to undertake a second round of pit stops, Hamilton leading the latest charge onto pit lane on lap 18 for a reversion to dry weather tyres.
It was increasingly surprising that there had still not been a safety car so far in the race with the number of incidents that had been seen and the amount of debris lying on the racing line dropping off from damaged cars - such as Sebastian Vettel's mangled Red Bull. One bit of debris punctured Rosberg's right rear tyre on lap 21 just after he'd pitted for new tyres, and finally the video evidence was too great for the race director to ignore. On lap 23, the safety car was at last deployed for the first time of the day.
That allowed Hulkenberg and Button to dive into pit lane for their first stops of the afternoon and still return to the track at the head of the field, essentially giving them both a free pit stop while the rest of the cars were still struggling to catch up while complying with their restricted delta times. The safety car closed up the field as a whole, and when racing resumed on lap 30 there was a clear dry line all round the circuit and everyone was back on dry tyres, although Alonso was reporting more rain at turn 4 and the weather service was now also forecasting more light rain as incoming.
Hulkenberg easily cleared for the lead ahead of Button, Hamilton and Alonso, but behind them there was a white knuckle moment for fifth which saw Vettel flanked by Webber on the outside and Kobayashi on the inside three-wide into turn 1. Kobayashi won the position, but there was a moment of career-defining realisation for Webber: if he turned in, he would wipe out his leader and championship leader Sebastian Vettel. He couldn't do it and expect to stay with the team, so he had to abort and slid off into the run-off, which dropped him down to a lowly fourteenth place y the time he rejoined the track.
Elsewhere, changing conditions were resulting in changing positions up and down the field. Hamilton got the better of Button for second place on turn 4 on lap 31, and next time round it was Kamui Kobayashi
getting the jump on Fernando Alonso
through the Senna esses for fourth place - only for the Ferrari
to undo the damage on lap 33. Sebastian Vettel
was in sixth behind this battle, clearly chomping at the bit to give it a go but being warned by his team to not stress his already-damaged car too much or else it could end in disaster. This time, Vettel realised the truth of the situation and complied, so that when he came under attack from Felipe Massa
he opted for discretion over fool-hardy valour and ceded the spot to the Brazilian, who quickly went on to pick up fifth place from Kobayashi for good measure.
Conditions still looked murky and grey as the race reached lap 40 an hour after the start, and a spin by Paul di Resta that dropped the Force India
down to 12th place emphasised just how tricky the conditions remained even though the rain was little more than a light drizzle. Mark Webber
also spun on lap 44 heading into Juncao after dabbing a tyre onto the still-wet white lines under braking, and Vitaly Petrov had a spin at Ferradura on lap 47, but it was no where near wet enough to even consider reverting to intermediates even though everyone was nearing end-of-life on their current set of dry tyres. The drivers would simply have to take extra-special care in the meantime, and not do anything silly.
That advice came too late for Nico Hulkenberg, who spun the Force India
at Pinheririnho on lap 48. While he quickly gathered the car up and resumed, it was too late to do anything about Lewis Hamilton
nipping through and claiming the lead. Hulkenberg was able to keep second place over Button, followed by Ferrari
team mates Alonso and Massa with Kobayashi still ahead of Vettel and Webber. As far as the world championship was concerned, that was still comfortably inside Red Bull's safety margin for getting Vettel his third championship.
But things were about to change again: the rain was actually getting heavier, resulting in Kimi Raikkonen
flying off from ninth place and going for a sightseeing excursion through the grassy infield. The conditions were also impeding Hamilton, and on lap 55 Hulkenberg sensed the possibility of reclaiming the lead when Hamilton found himself held up by the Marussia of Timo Glock. Hulkenberg attempted the inside line, but the tyres couldn't take it on the greasy track and dug in, hopping the Force India
into the air - and the back end of the car landed right on top of the front left suspension of the McLaren, which was demolished by the impact. For this third time in 2012, Hamilton had gone from leading the race to retirement in a matter of seconds.
That put Button back into the lead ahead of the Ferraris while Hulkenberg was dumped down to fifth behind Webber after being handed a penalty for causing the collision with Hamilton.
Meanwhile Sebastian Vettel
was dumped briefly out of the top ten as the result of a poor pit stop for Vettel, partly the rest of problems with radio communications between the car and pit wall which meant they were ill-prepared when Vettel came in for an emergency new set of intermediates having pitted just a few laps previously for medium compound slicks.