Spanish GP P1: Nico Rosberg fastest from Lewis Hamilton

Nico Rosberg set the pace in first practice for the Spanish GP as F1 returned to action after its three-week break on Friday.

The German topped the timesheets with a lap of 1:26.828 with world champion Lewis Hamilton less than a tenth of a second adrift of his Mercedes team-mate.

Rosberg had been placed under investigation by the Barcelona stewards after making an illegal entry into the pitlane when his Mercedes crossed the line after the safety bollard.

A sporting punishment - such as a grid demotion - for the infringement was a possibility but instead Rosberg escaped with a reprimand.

Despite the avalanche of new parts bolted on to the cars, it was business as usual at the front with Mercedes maintaining a one-second advantage over Ferrari, for whom Sebastian Vettel and Kimi Raikkonen were third and fourth respectively ahead of the Toro Rossos of Carlos Sainz and Max Verstappen.

"We’ve brought several updates aerodynamically," Mercedes chief Paddy Lowe told Sky Sports F1. "But I don’t think that will be unusual; most teams will bring a lot of updates to this race. It’s actually more about whether you’ve brought more or less performance than the other teams. And we don’t really know that until qualifying and the race.” 

Ferrari are believed to have tested up to 16 new parts on their car while Daniil Kvyat Red Bull's sported an ultra-short nose. The Russian was seventh quickest, two places ahead of stable-mate Daniel Ricciardo with the Australian already using the fourth of his four permitted penalty-free engines this season.

Meanwhile, making her first appearance of the season, Susie Wolff was just 14th fastest for Williams, but less than second slower than team-mate Felipe Massa.

However, Jolyon Palmer impressed for Lotus, out-pacing the under-pressure Pastor Maldonado as the GP2 champion substituted for Romain Grosjean. It was the first time in his three outings so far this year that the young Englishman has finished ahead of Maldonado.

But there appears to be no end in sight for McLaren's struggles with Fernando Alonso and Jenson Button a modest 15th and 16th in the new-look McLarens. Despite its relaunch in a new livery, the MP4-30 still appeared to be a handful for both former world champions, with the team's long-awaited breakthrough still seemingly no closer to fruition.

Practice One timesheet:

1. Nico Rosberg, Mercedes, 1:26.828

2. Lewis Hamilton, Mercedes, 1:26.898

3. Sebastian Vettel, Ferrari, 1:27.806

4. Kimi Raikkonen, Ferrari, 1:27.832

5. Carlos Sainz, Toro Rosso, 1:28.132

6. Max Verstappen, Toro Rosso, 1:28.529

7. Daniil Kvyat, Red Bull, 1:28.785

8. Felipe Massa, Williams, 1:28.831

9. Daniel Ricciardo, Red Bull, 1:29.075

10. Felipe Nasr, Sauber, 1:29.140

11. Nico Hulkenberg, Force India, 1:29.409

12. Raffaele Marciello, Sauber, 1:29.630

13. Jolyon Palmer, Lotus, 1:29.676

14. Susie Wolff, Williams, 1:29.708

15. Fernando Alonso, McLaren, 1:29.813

16. Jenson Button, McLaren, 1:29.817

17. Sergio Perez, Force India, 1:30.096

18. Pastor Maldonado, Lotus, 1:30.110

19. Will Stevens, Manor, 1:32.471

20. Roberto Merhi, Manor, 1:32.647