Jenson happy on 'home' straight

For Button, the opening Grand Courbe turn is one of the most exciting because it is taken flat out at 280kph after the start- finish straight. Drivers must get the line correct into the corner because it leads to the equally tricky Estoril curve, a fourth-gear corner over a crest. He said: "At the start of the lap there is a very fast left-hand corner and you take it in top gear at 280 kph. It is quite easy to take flat out but you need to position the car well as it leads into quite an important right-hand corner.

"You approach the next corner, Estoril, at just under 290 kph and due to the slope almost take the two apexes through it."

After the twisty infield section including the Adelaide hairpin and the Imola chicane, Button brings the lap to a close through another difficult part of the track.

The third chicane, just before the final Lycee corner, must be negotiated after approaching over a brow and it is vital to get the apex right or risk a trip into the gravel.

"The final chicane is much slower than the previous two and is taken in second gear but on exit you don't get to full throttle because you have to brake for the final very tight corner," Button added.

"The start-finish line is very close to the exit of the corner and for a good qualifying lap you need to pay particular attention to the exit in order to cross the finish line at around 140 kph."

Button is aware of the significance of the race for Renault. "It is obviously important for everyone in the team to do well in this race," he said.

If Button leaves for either Sauber or Toyota, meanwhile, it could be bad news for Allan McNish.

He will be a straight replacement for the Scot if he joins Toyota. If Sauber is his next stop, it is likely to be as replacement for Germany's Nick Heidfeld, who would then almost certainly be moving to Toyota to partner Mika Salo, leaving McNish high and dry.