Lewis Hamilton won an action-packed Japanese Grand Prix and took a huge step towards becoming the first rookie to win the Formula One driver's world championship after Fernando Alonso, his McLaren team-mate and fiercest rival, failed to finish at a sodden Fuji Speedway.

The 22-year-old overcame terrible conditions, two safety car periods and all manner of incidents with a mature drive to claim his fourth win of the season and open up a 12-point lead over Alonso at the top of the drivers' standings with just two races to go. Victory in Chna next week could secure the title for Hamilton.

Alonso saw his title chances all but washed away after losing control of his car on lap 42 and crashing into the safety barrier, while Kimi Raikkonen, the Ferrari driver, kept his slim hopes alive by finishing third.

"It was the longest race of my life, it went on and on," Hamilton said. "The last few laps the team was telling me to slow down but I was still second fastest. But I took it really easy because it would have been easy to take it off. But I'm delighted to win, thrilled for the team."

Hamilton added: "It was a very, very eventful race. There were so many times when it must have gone through all the drivers' heads that we should have stopped. We had the safety car at the beginning. After that I got off to a decent start and didn't feel any pressure, and could have pushed more."

Alonso, the reigning world champion, refused to blame the conditions for his crash but admitted he now needed a miracle to overhaul Hamilton in China and Brazil.

"It's very easy to say now if [the conditions] is good or not but I was happy to start the race - we are here to race, we are drivers. It was the same for everybody," he said.

"It is not over because mathematically it has to be over. But I need a very unlucky weekend for [Hamilton] to have a chance to win. If it is a normal race, it is over."

Continuous rain had left large amounts of standing water on the 4.563km circuit, and with the possibility of a serious accident as the cars sped down to a tight turn one enveloped in spray, the race organisers decided to order a safety-car start with Hamilton leading the grid off in formation. And the treacherous conditions saw Ferrari's Felipe Massa spin on just the second lap before heading into the pits for extreme weather tyres.

Raikkonen, Massa's team-mate, also came in at the end of lap three to change tyres, meaning the two Ferraris were now running 20th and 21st. Raikkonen then left the circuit on lap six before pitting a second time at the end of lap 14 while Massa also took on fuel and changed tyres shortly afterwards.

But the safety car came in at the end of lap 19 and, after a game of cat and mouse between Hamilton and Alonso in the run-up to the start-finish straight, it was the Brit who led after the first corner.

Hamilton quickly opened up some breathing space over his championship rival, while Massa's afternoon took a turn for the worse with a drive-through penalty for overtaking under the safety car before the Brazilian was hit by Alex Wurz at turn one after the Austrian had lost control of his Williams on the home straight.