Mark Webber was quickest of a very competitive first practice session for the Brazilian Grand Prix.
Webber's time of 1:13.811 edged out Jenson Button's McLaren by just 0.014s , with Lewis Hamilton the only other man to dip below the 1m14s barrier. Sebastian Vettel was fourth, just 0.214s slower than Webber, with Felipe Massa fifth and Fernando Alonso - who had to stop late in the session with an engine failure - sixth.
All of the times were set on the medium compound tyres as teams spent the morning testing a potential hard tyre for 2012 as well as new parts, while there were no fewer than five replacement drivers taking part in the session.
One such driver - Jan Charouz - on his debut, ran wide at turn one as he explored the track limits in the F111. He was far from the only drive to run off the track though, as Kamui Kobayashi had a spin at turn 10, losing the rear as he struggled to turn in having got wide in turn 9. He rolled back on to the circuit but quickly spun the car back round to get out of the way of other cars and continue.
Jaime Alguersuari was another driver to run off track as he had to recover from running wide out of turn four and missing turn five, while Vettel followed suit soon after.
Romain Grosjean was doing another impressive job for Renault until he stalled at the end of the pit lane, leaving him to have to sit out the final 25 minutes of the session. He still managed to end the session quicker than Bruno Senna though, as Nico Hulkenberg also outpaced Paul di Resta.
With ten minutes left in the session Alonso was cruising down the pit straight and came on the radio to ask the team to check the engine. He rolled down the hill to turn two, doing well to keep out of the way of traffic before parking the car on the outside of the corner with what Ferrari confirmed was an engine failure. It will not have made a bit impact on the session plan for the team, but Alonso will have to switch to his race engine earlier than planned.