Austrian GP: Valtteri Bottas grabs practice top spot for Williams

The Finn had shown well during the early stages of the session, ending up second fastest on soft-compound pace on a strong weekend for Williams.

But Lewis Hamilton had looked set to top the times for Mercedes when he knocked the other Williams of Felipe Massa off top spot by three thousandths of a second with four minutes of the hour remaining.

Bottas then strung together a superb final lap, including the fastest final sector of the session, to go fastest by just five hundredths of a second.

Toro Rosso's Daniil Kvyat also put in an impressive late lap to go fourth fastest, with Nico Rosberg ending up fifth having earlier set the pace when the field was running on the soft-compound Pirellis.

A tight qualifying session is expected this afternoon, with Fernando Alonso down in sixth but only two tenths slower than Bottas.

Red Bull's taxing weekend continued, with Daniel Ricciardo half a second off the pace in sixth place, while team-mate Sebastian Vettel was 10th, seven tenths down.

Sandwiched by the Red Bulls were Kevin Magnussen and Kimi Raikkonen.

Jenson Button had a frustrating session, running off track at Turn 1 and complaining about a lack of engine braking.

McLaren discovered that he had a problem with the right-rear brakes, meaning it had to change the calliper as well as replacing the floor, which was damaged when Button went off.

The 2009 Formula 1 world champion managed only four laps during the session and was unable to post a serious time, meaning he ended up slowest.

Pos  Driver             Team/Car              Time       Gap      Laps
 1.  Valtteri Bottas    Williams-Mercedes     1m09.848s           22
 2.  Lewis Hamilton     Mercedes              1m09.898s  +0.050s  25
 3.  Felipe Massa       Williams-Mercedes     1m09.901s  +0.053s  21
 4.  Daniil Kvyat       Toro Rosso-Renault    1m09.927s  +0.079s  25
 5.  Nico Rosberg       Mercedes              1m09.999s  +0.151s  31
 6.  Fernando Alonso    Ferrari               1m10.054s  +0.206s  17
 7.  Daniel Ricciardo   Red Bull-Renault      1m10.392s  +0.544s  19
 8.  Kevin Magnussen    McLaren-Mercedes      1m10.449s  +0.601s  23
 9.  Kimi Raikkonen     Ferrari               1m10.488s  +0.640s  22
10.  Sebastian Vettel   Red Bull-Renault      1m10.562s  +0.714s  21
11.  Nico Hulkenberg    Force India-Mercedes  1m10.683s  +0.835s  22
12.  Pastor Maldonado   Lotus-Renault         1m10.776s  +0.928s  26
13.  Jean-Eric Vergne   Toro Rosso-Renault    1m11.043s  +1.195s  22
14.  Romain Grosjean    Lotus-Renault         1m11.103s  +1.255s  22
15.  Sergio Perez       Force India-Mercedes  1m11.235s  +1.387s  18
16.  Adrian Sutil       Sauber-Ferrari        1m11.294s  +1.446s  24
17.  Esteban Gutierrez  Sauber-Ferrari        1m11.558s  +1.710s  23
18.  Jules Bianchi      Marussia-Ferrari      1m11.848s  +2.000s  21
19.  Kamui Kobayashi    Caterham-Renault      1m12.320s  +2.472s  23
20.  Marcus Ericsson    Caterham-Renault      1m12.892s  +3.044s  27
21.  Max Chilton        Marussia-Ferrari      1m12.915s  +3.067s  14
22.  Jenson Button      McLaren-Mercedes      1m14.237s  +4.389s   4