Somerset driver Jenson Button was beaming once again despite the rain as he made it back-to-back victories in the 2009 Formula One season in a "crazy" Malaysian Grand Prix.

The Brawn GP driver was leading on the 33rd of 56 scheduled laps when the race had to be red-flagged due to monsoon conditions at the Sepang circuit.

With the torrential rain refusing to relent and darkness descending on the track due to the late start time, organisers eventually decided not to restart the race, awarding half-points to the top eight finishers.

The race results were counted back to the 31st lap and Button was awarded first place and five points after finishing 22.722 seconds ahead of BMW Sauber's Nick Heidfeld, who took second after deciding to stay out slightly longer on his extreme wet tyres.

Timo Glock was third for Toyota a further eight-tenths of a second behind Heidfeld after a strong run in intermediates during a period before the heavens fully opened.

Jarno Trulli was fourth in the second Toyota, Button's Brawn GP team-mate Rubens Barrichello finished fifth and Red Bull's Mark Webber was sixth in the first race to be shortened because of poor weather since the 1991 Australian Grand Prix in Adelaide.

Reigning world champion Lewis Hamilton enjoyed some consolation after a difficult week by finishing seventh for McLaren, while Nico Rosberg gained the final half-point by finishing eighth for Williams.

It was an eventful outing for Button, who now leads the world championship standings with 15 points, five ahead of Barrichello.

"What a crazy race," said the 29-year-old, who started on pole position but dropped to fourth after the first sequence of corners as he was passed by Rosberg, Trulli and the Renault of Fernando Alonso.

"My start was pretty bad, I had a lot of oversteer in the car and I don't think I got heat into the rear tyres. I went back to fourth, got back up to third and eventually got back to the front and I was pretty happy."

Button reclaimed third place from Alonso's fuel-heavy Renault before the end of the first lap and moved back into the lead after Rosberg and Trulli pitted, holding on to the advantage after pitting himself for the first time.

But everything changed when the rain finally arrived on lap 22 with many of the drivers pitting again and electing to go straight to extreme wet tyres.

Glock, who opted not to change, was able to make up tremendous ground on the rest of the field as the expected downpour did not materialise immediately.

"Our pace was good and then the rain started," said Button.

"Choosing the tyres became difficult because when it rains here it usually pours, but it didn't to start with. We went for the full wet tyre and it just destroyed itself.

"I saw Timo flying up behind us on the intermediates so we put the inter on. Just as he came by I saw his tyres were bald. It was raining out the back so he had to pit.

"I was then able to get one lap in at reasonable pace before I had to pit and was able to get back out in front.

"It was a very interesting race but I still haven't seen a chequered flag without a safety car."

Heidfeld claimed second place and four championship points after battling his way from 10th on the grid, thanks to a fortuitous decision to stay out slightly longer on his wet tyres.

"It was very difficult to make choices in these conditions," he said.

"I didn't make the perfect tyre choices as I went straight to extras as there is normally heavy rainfall here.

"The team then told me there was heavy rain expected but I told them intermediates would be quicker and then when they told me to pit, it started to rain heavier and it was just 200m from the pit entry so I decided to stay out and preserve my tyres."

Glock, who started third on the grid, was pleased his tyre gamble paid off as he secured only the second podium of his career.

"It was a tricky race. In the end it was one of the best races I have ever had," said the German.

"After five or six laps I saw the clouds and I kept asking when the rain was coming and they said it should come in the next few minutes. But it took so long and you could see the big clouds coming.

"It took so long and we were so close to the first pit stop so we decided to take the risk and go for intermediates because Felipe Massa was on heavy wets very early, and I knew they would destroy very easily. So we went for the inters and took the risk and it paid off."

Trulli remained third in the drivers' championship standings after claiming 2.5 points for fourth place finish.

The result also kept Toyota in second place in the constructors' championship with 16.5 points, 8.5 behind leaders Brawn GP.