Ahead of today's second free practice session the air temperature is 16 degrees C, while the track temperature has risen to 38 degrees.

First out is Christian Klien, followed by Robert Doornbos, Pedro de la Rosa, Kimi Raikkonen, Ricardo Zonta and Tonio Liuzzi.

The Austrian posts the first time of the afternoon, crossing the line at 1:26.202, though moments later de la Rosa goes quickest with a 1:24.230.

A 1:22.945 sees Kimi Raikkonen take over at the top of the timesheets, as Coulthard, Massa and the two Ferrari drivers leave their garages.

Raikkonen improves with a 1:22.258 as Zonta goes third and DC a disappointing seventh, 7s off the pace.

Next time around, the Scot posts a more serious 1:24.740, no doubt prompted by Liuzzi's 1:26.161.

Suddenly all hell breaks loose as a whole load of big guns come out for a real assault on the benchmark. Once the dust has settled, Jenson Button is on top, ahead of Raikkonen, Sato, Michael, Wurz, Barrichello and de la Rosa.

Fisichella has posted his first time of the day, but it's only good enough for eighth, ahead of Massa and Trulli.

With thirteen minutes gone, Alonso, the WilliamsF1 duo and Albers are the only drivers yet to post a time.

After the earlier frenzy of activity, it now goes quiet, though de la Rosa and Coulthard both improve.

A 1:22.048 sees Barrichello go second, though the Ferrari driver is still almost a second off Button's time.

Almost unnoticed, Giancarlo Fisichella goes third with a 1:22.211, meanwhile Heidfeld and Webber finally make an appearance.

As Webber goes sixteenth, and Heidfeld fourteenth, Patrick Friesacher, for the first time today, gets within 5s of the benchmark.

At the halfway point, in what is really quite a tedious session, Button remains quickest, ahead of Barrichello, Fisichella, Raikkonen, Sato, Michael, Wurz, de la Rosa, Zonta and Massa. The Toyotas are eleventh (Trulli) and fifteenth (Ralf), prompting the thought that perhaps the Japanese outfit's chassis isn't coping with Imola's unforgiving kerbs in quite the way it had been hoped.

Finally, after 100 minutes of the San Marino GP weekend, Fernando Alonso leaves his garage, hopefully to finally post a time.

His first lap sees the Spaniard go eleventh (1:23.221), next time around he goes seventh with a 1:22.912.

Moments later, the Renault driver is bumped down, when Wurz goes fourth with a 1:22.174.

With just over seven minutes remaining, Button is still quickest ahead of Raikkonen, Barrichello, Wurz, Fisichella, Sato, Michael, Alonso, Massa and Villeneuve.