Marrussia driver Max Chilton recorded the fastest time on the first day of testing in Barcelona on Tuesday on a day that was interrupted on several occasions.
Chilton's time of 1:26.434 was set on the super-soft tyres in the final seconds of the session, and was more than two tenths quicker than the Lotus of Charles Pic, who seemed like he would top the time sheets at the end of the first day in Barcelona when he posted a time of 1:26.661.
Lewis Hamilton was third fastest after posting a series fastest laps during the final 30 minutes of the session, the quickest of which was just 13 thousands of a second slower than that of the Lotus driver.
Earlier, Kimi Raikkonen was the first driver to record a sub 1.27s time when his Ferrari took a liking to the soft Pirellis to record a 1:26.965.
During a day that was interrupted by rain earlier in the day and several red flag incidents later on, Jean-Eric Vergne was fourth fastest in his Toro Rosso, although he was almost eight tenths slower than the Finn.
Toro Rosso is one of two teams - Sauber the other - that is testing some new rubber for Pirelli, and the Frenchman needed three attempts to finally post a time after coming unstuck at Turn 10 and then Turn 4.
The Frenchman's time was just three thousands faster than the best of Nico Hulkenberg in the Force India, who did very little running early in the morning session that was curtailed by wet weather.
The Williams of Felipe Massa was seventh fastest, almost a second slower than Chilton, with Jenson Button, Kamui Kobayashi, Sebastien Buemi and Giedo van der Garde the other drivers to complete laps on the day.
Despite posting what seems to be a competitive time, Ferrari and Raikkonen had another troubled day.
During Raikkonen's second lap, his F14T was engulfed with smoke and he was forced to stop on track, before ending his day in the gravel at Turn 4 after completing just 12 more laps during the afternoon session.
Apart from the red flags after the incidents involving Vergne and Raikkonen, Buemi also caused an incident when his Red Bull suffered a gearbox problem and was forced to stop between Turn 6 and 7, which ended his day prematurely.
Day One lap times:
1. Max Chilton Britain Marussia-Ferrari 1m 26.434s
2. Charles Pic France Lotus-Renault 1m 26.661s
3. Lewis Hamilton Britain Mercedes-Mercedes 1m 26.674s
4. Kimi Raikkonen Finland Ferrari-Ferrari 1m 26.965s
5. Jean-Eric Vergne France Toro Rosso-Renault 1m 27.724s
6. Nico Hulkenberg Germany Force India-Mercedes 1m 27.727s
7. Felipe Massa Brazil Williams-Mercedes 1m 27.756s
8. Jenson Button Britain McLaren-Mercedes 1m 28.333s
9. Kamui Kobayashi Japan Caterham-Renault 1m 30.101s
10. Sebastien Buemi Switzerland Red Bull-Renault 1m 31.440s
11. Giedo van der Garde Netherlands Sauber-Ferrari 1m 31.783s