Button tops second Australia practice

The session, which was run under race conditions for the last 30 minutes to test out the new overtaking zone, saw most of the fastest running take place, predictably, just before the hour mark when everyone tried the soft Pirelli 'Option' tyre.

It was during this period that first Hamilton posted a 1m25.854s, and then Button improved upon it to go 0.132s faster still. Whether or not McLaren's pace is a true measure of the overall picture remains unclear however, for Red Bull's drivers, who dominated session one, were instructed not to use their adjustable rear wings for much of the session.

In the end, Sebastian Vettel and Mark Webber were unleashed, once they got on to the Option tyres, but neither could match Fernando Alonso's Ferrari, which ended the session third.

Michael Schumacher improved to sixth fastest in the Mercedes, having been fastest of all for a while. Felipe Massa, one of several drivers to run off-track during the session, was seventh.

Mexican rookie Sergio Perez was an impressive eighth fastest on his first grand prix day for Sauber, outpacing the sport's most experienced driver Rubens Barrichello, who was ninth for Williams - another to test the gravel run off at Turn 3.

Nico Rosberg completed the top ten for Mercedes ahead of Jaime Alguersuari's Toro Rosso and Vitaly Petrov in the Renault.

Another rookie, Paul di Resta deserved credit for outpacing team-mate Adrian Sutil in 16th, while Pastor Maldonado was 18th on his first practice day for Williams.

It was not a stellar session for F1's newest teams. Both Lotus cars were the best part of five seconds off the pace, while the Virgins reduced the deficit to front from more than eight seconds in the morning to seven seconds in the afternoon.

HRT, which announced early in the session that it intended to complete installation laps only, managed to get Tonio Liuzzi out on track with two minutes remaining.

The test of drag reduction systems in the last half an hour of practice provided little indication of what might be to come in the race, and eventually was brought to a premature conclusion when rain began to fall in the last 10 minutes.

Pos  Driver         Team                   Time              Laps
 1.  Button         McLaren-Mercedes      1m25.854s            32
 2.  Hamilton       McLaren-Mercedes      1m25.986s  + 0.132   31
 3.  Alonso         Ferrari               1m26.001s  + 0.147   28
 4.  Vettel         Red Bull-Renault      1m26.014s  + 0.160   35
 5.  Webber         Red Bull-Renault      1m26.283s  + 0.429   33
 6.  Schumacher     Mercedes              1m26.590s  + 0.736   31
 7.  Massa          Ferrari               1m26.789s  + 0.935   34
 8.  Perez          Sauber-Ferrari        1m27.101s  + 1.247   39
 9.  Barrichello    Williams-Cosworth     1m27.280s  + 1.426   34
10.  Rosberg        Mercedes              1m27.448s  + 1.594   23
11.  Alguersuari    Toro Rosso-Ferrari    1m27.525s  + 1.671   31
12.  Petrov         Renault               1m27.528s  + 1.674   29
13.  Heidfeld       Renault               1m27.536s  + 1.682   22
14.  Buemi          Toro Rosso-Ferrari    1m27.697s  + 1.843   30
15.  Kobayashi      Sauber-Ferrari        1m28.095s  + 2.241   35
16.  di Resta       Force India-Mercedes  1m28.376s  + 2.522   33
17.  Sutil          Force India-Mercedes  1m28.583s  + 2.729   31
18.  Maldonado      Williams-Cosworth     1m29.386s  + 3.532   29
19.  Kovalainen     Lotus-Renault         1m30.829s  + 4.975   22
20.  Trulli         Lotus-Renault         1m30.912s  + 5.058   23
21.  D'Ambrosio     Virgin-Cosworth       1m32.106s  + 6.252   36
22.  Glock          Virgin-Cosworth       1m32.135s  + 6.281   30
23.  Liuzzi         HRT-Cosworth          No time               1

All Timing Unofficial