Reigning Formula One world champion Sebastian Vettel stole the fastest lap from under the nose of Fernando Alonso on the first day of the penultimate winter test at Barcelona's Circuit de Catalunya, Spain.
Following heavy rain on Thursday, the track took until lunchtime before drying out enough to allow any meaningful lap times to be set.
The circumstances surrounding the track made the session potentially the most difficult to gain any understanding of performance and the majority of quick lap times were set during short exploratory laps. The circuit was warming up and ready for slick tyres while the afternoon was largely spent focusing on long runs and accumulating as many laps as possible.
Vettel's 1m24.374s lap was the first time a Red Bull had topped the time sheets this year and despite completing a mere 27 laps in total, the German was frustrated at his lack of running but remained optimistic for Saturday's running.
"Unfortunately, we didn't complete many laps today, as we had a long break - longer than expected," Vettel said. "It wasn't anything big, nothing broke, but at the test if you think there might be a problem then you'd rather take the car apart and check. The boys did their best and we still got some runs towards the end of the day - not as much as we'd like, but the car feels good and hopefully we'll do more tomorrow."
Racking up the most amount of laps for the day, Fernando Alonso's 1m25.485s looked certain to keep him at the top of the standings until Vettel's late surge with nine minutes to go. The Spaniard was unconcerned as his focus was on collating more data as the team continue to press on development of the 150th Italia.
"Overall, it was a positive day," said Alonso. "We did a lot of laps and brought home much valuable information. It seems that, on this track too, there is a certain level of tyre degradation, but it is only the first day and we have to see how the track evolves between now and Monday."
Once again, Jamie Alguersuari and Kamui Kobayashi set competitive times for Toro Rosso and Sauber respectively, ending the day in third and fourth. Despite their relatively strong performances, they both caused red flags with the Toro Rosso spinning into the Turn 4 gravel and the Sauber stopping on the circuit during a fuel consumption evaluation - the same as they did in Jerez last week.
Jenson Button undertook the driving duties for McLaren, taking fifth fastest lap on another quiet day for the Woking-based team. The 2009 champions best lap of 1m26.365s was another indication of a potential lack of stability with the MP4-26 yet perhaps of more importance was that he was able to complete 77 relatively trouble free laps and the team were able to run their drag reduction system for the first time in anger.
Waiting the majority of the morning for new parts to arrive, Force India's Paul di Resta was only able to get serious running in the afternoon yet the Scottish rookie was able to set a best of1m26.575s despite only completing 26 laps in total.
"The guys did pretty well to get the car out on track today," di Resta said. "Towards the end of the afternoon we did some productive running to get a good baseline set-up for tomorrow when we'll have a much more extensive test programme to carry out. I definitely feel there is more to come from the car and I'm looking forward to getting back out there to help the team get as much out of this test as possible."
Another frustrating day at Williams saw Rubens Barrichello cause a red flag just before the lunch break before a precautionary engine change sidelined him for the majority of the afternoon, resulting in the seventh fastest time of 1m26.912s and a total of 52 laps.
Spending the majority of the afternoon completing a race simulation in the Mercedes MGP - 02, Michael Schumacher set the eighth fastest lap with a 1m27.512s with Narain Karthekeyan in the HRT in ninth position on a 1m28.393s.
Heikki Kovalainen was tenth for Team Lotus ahead of Jerome D'Ambrosio in the Virgin. Sharing the driving duties for Lotus Renault GP, Vitaly Petrov and Nick Heidfeld finished twelfth and thirteenth respectively on what proved to be a difficult day for the team with both men amassing only 47 laps combined.