Jenson Button has admitted that there were moments when he feared his hard work in the Chinese Grand Prix could be undone, but insists that there was no luck involved in his second win for McLaren.

The Briton again used inspired decisions on tyres in changeable conditions to move to the front of the field in Shanghai, and was building a lead when the safety car appeared for a second time to remove debris from Jaime Alguersuari's Toro Rosso, allowing the rest of the field, including a flying Lewis Hamilton to close back in.

"I had my heart in my mouth when that happened, as I just did not know what was going to happen," Button confessed, "We had built up such a good gap and then, unfortunately, everyone else caught up, so it made it very tricky. If we didn't have that safety car, we would have been a long... well, I don't know. I don't know how quick Lewis was in the race, but the safety car definitely helped the situation for people that stopped for inters."

The race was thrown into confusion by the arrival of rain shortly after the start. Although everyone knew that there was a strong possibility of precipitation, it was its timing that remained unknown and, although there were initial spots while the grid was forming up, it wasn't enough for wholesale changes before racing began. Only Toro Rosso's Sebastien Buemi started on intermediates, but the Swiss driver was joined by most of the field on lap two as the rain intensified.

Button was among the handful of pilots to stay out, jumping to second place behind Mercedes' Nico Rosberg, and the world champion's decision was justified as those that had changed were forced to return to the pits just a couple of laps later. That second stop helped the leaders extend their advantage, and it was only the re-appearance of the safety car that prevented Button, who subsequently passed Rosberg on the road, from taking a more comfortable win.

Once again, as had been the case in Australia, the Briton revealed that he had been in charge of his own destiny.

"We discussed it on the radio, and they said 'pit this lap if you feel it's too wet,' so I decided to stay out," he explained, "Then, later on in the race, they made the call to go to inters, which was definitely the right call. I was thinking of staying out again and they made the right call there. I think what won us the race today was the right calls for the right conditions and being on the right tyre at the right time. It makes such a difference.

"I felt that it was the right thing to do, to stay out. A few other drivers did it as well, so I wasn't alone in that one. I'm sure I will make the wrong calls as well - it doesn't always happen that you get the right call - but sometimes you've got to take those risks. That's what we did and it paid off again."

Even though he acknowledged that intermediates were the right choice for the closing stages, Button again admitted to fearing for his victory as the tread wore away and left him vulnerable to the conditions.

"It was pretty damn good I must say - except for the last four laps," he conceded, "They were a little bit scary. It was raining a lot at the end, and I was really struggling with the tyres. I pulled a good gap on Lewis, but maybe I pushed the tyres a bit hard and, when it rained, I was just skating all over the place and as you saw, I went straight on at the hairpin. I made it difficult for myself - I had my heart in my mouth while I was trying to keep the thing on the road - so it's great to come away with a victory."