Lewis Hamilton set the pace for the opening Formula 1 practice session of the Spanish Grand Prix weekend to continue his stronghold on this year's championship.
The Mercedes driver ensured it was a British 1-2 at the top of the timing sheets as he finished 0.868s ahead of McLaren's Jenson Button.
Button held the fastest time for the majority of the Friday morning session recording his best time on the hour mark.
The McLaren driver was stationed at the top of the timesheets until his compatriot Hamilton set the fastest time five minutes from the end of the session.
There were problems for Sebastian Vettel, who sat out nearly the entire practice period after an electrical issue halted his running and he pulled to the side of the track at Turn 5, just 25 minutes into FP1.
The German had only completed four laps when the problem struck his car and he ended up with the 20th fastest time.
Nico Rosberg could only manage the fifth fastest time after he suffered a lack of running due to a problem with his Mercedes power unit.
Behind Button, Daniel Ricciardo was third fastest in his Red Bull ahead of Fernando Alonso, who was visibly hustling his Ferrari around the Spanish GP circuit.
His team-mate Kimi Raikkonen was sixth ahead of the second McLaren of Kevin Magnussen.
There was drama for Giedo van der Garde when he suffered a partial brake failure at Turn 1 and ran through the gravel at high speed, just missing the barriers on the outside of the corner.
Sauber's reserve driver was in the car in place of Esteban Gutierrez for FP1. He was able to continue to the pits unharmed.
The opening practice session of the weekend was the first chance for all the teams to try test the performance of their upgrades.
There was a bizarre moment for Sergio Perez when his left rear view mirror broke and came into his cockpit, forcing the Force India driver into the pits.
Pos Driver Team Time Gap Laps 1. Lewis Hamilton Mercedes 1:27.023s 17 2. Jenson Button McLaren-Mercedes 1:27.891s +0.868s 26 3. Daniel Ricciardo Red Bull-Renault 1:27.973s +0.950s 21 4. Fernando Alonso Ferrari 1:28.128s +1.105s 23 5. Nico Rosberg Mercedes 1:28.168s +1.145s 9 6. Kimi Raikkonen Ferrari 1:28.337s +1.314s 19 7. Kevin Magnussen McLaren-Mercedes 1:28.423s +1.400s 27 8. Pastor Maldonado Lotus-Renault 1:28.744s +1.721s 34 9. Sergio Perez Force India-Mercedes 1:28.779s +1.756s 18 10. Felipe Massa Williams-Mercedes 1:28.791s +1.768s 13 11. Daniil Kvyat Toro Rosso-Renault 1:28.792s +1.769s 24 12. Nico Hulkenberg Force India-Mercedes 1:28.828s +1.805s 17 13. Jean-Eric Vergne Toro Rosso-Renault 1:28.859s +1.836s 24 14. Felipe Nasr Williams-Mercedes 1:29.272s +2.249s 15 15. Adrian Sutil Sauber-Ferrari 1:29.688s +2.665s 16 16. Jules Bianchi Marussia-Ferrari 1:29.820s +2.797s 22 17. Romain Grosjean Lotus-Renault 1:29.444s +2.421s 21 18. Giedo van der Garde Sauber-Ferrari 1:30.440s +3.417s 21 19. Max Chilton Marussia-Ferrari 1:30.748s +3.725s 19 20. Sebastian Vettel Red Bull-Renault 1:30.942s +3.919s 4 21. Kamui Kobayashi Caterham-Renault 1:30.997s +3.974s 22 22. Marcus Ericsson Caterham-Renault 1:31.421s +4.398s 22