Turkish Grand Prix - Button on top after Day 1

An eventful first day of practice at Istanbul ended with Jenson Button setting the fastest time, with team mate Lewis Hamilton fourth.

The Red Bull cars look very fast but there are reliability worries. Winner of the last two Grands Prix Mark Webber stopped out on track in the final moments of practice with a suspected engine failure, having set the second fastest time. It will have been an old engine, probably close to its mileage limit, but nevertheless and engine failure is an engine failure. His Red Bull team mate Sebastian Vettel was third fastest despite time lost to replace a water pipe and some wider concerns about water pressure.

Red Bull trialled their new drag reducing rear wing and will make a decision on whether to race it this weekend, or whether to take the learnings from today forward to the Canadian Grand Prix, where it will be indispensable.

The McLarens looked fast all day. McLaren's drag reducing rear wing was working well for them, Button and Hamilton were top of the speed trap times at 311km/h.

The afternoon session took place in blisteringly hot conditions, with a track temperature of 52 degrees.

Most of the running was done on the hard tyre from the Bridgestone range, but the fast times were set on the soft tyre, which has the speed on its first flying lap.

The multi-apex Turn 8 proved a real challenge for the drivers with many of them spinning or going off.

The most spectacular was the accident of Adrian Sutil in the Force India, equipped with a new drag reducing rear wing. He had a heavy impact with the barriers on the exit of the corner.

His team mate Tonio Liuzzi had a big spin there in the afternoon, but he wasn't the only one; Felipe Massa had three moments there, one of which destroyed his set of soft tyres.

Meanwhile Kobayashi and Petrov also found that the slightest mistake in the early part of the corner, particularly on the bump, will send the car off its trajectory.

In contrast the Red Bull cars looked very fast through Turn 8, the extra downforce they have giving them a very stable car through there. Webber's fastest Middle sector time was half a second quicker than either of the McLaren drivers. But the McLaren made up for it with its pace on the long straights and in the first sector.

Further back, Lotus showed signs of more progress, Heikki Kovalainen setting a time just 6/10ths of a second slower than the midfield team, the Toro Rosso of Jaime Alguersuari. His time was 1.4 secs faster than the Virgin of Lucas di Grassi.

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Turkish Grand Prix practice

1. Button McLaren-Mercedes 1:28.280 30

2. Webber Red Bull-Renault 1:28.378 + 0.098 24

3. Vettel Red Bull-Renault 1:28.590 + 0.310 26

4. Hamilton McLaren-Mercedes 1:28.672 + 0.392 32

5. Alonso Ferrari 1:28.725 + 0.445 30

6. Rosberg Mercedes 1:28.914 + 0.634 22

7. Schumacher Mercedes 1:28.974 + 0.694 22

8. Kubica Renault 1:29.225 + 0.945 34

9. Petrov Renault 1:29.501 + 1.221 36

10. Massa Ferrari 1:29.620 + 1.340 26

11. Sutil Force India-Mercedes 1:29.629 + 1.349 16