Spanish GP: Hamilton leads Mercedes F1 team-mate Bottas in FP1

Hamilton clocked a 1m21.521s on the medium tyre, finishing just 0.029 seconds quicker than team-mate Valtteri Bottas at Barcelona.

Ferrari's Kimi Raikkonen was the closest challenger to Mercedes, which is running radical scoop vanes on the nose, but he was nearly a second adrift.

The Mercedes drivers were evenly matched throughout the session, with Hamilton holding the edge by 0.089s on the early runs on the hard tyre.

After their first flying laps on the mediums, Hamilton and Bottas did a cool down lap before going again, but both failed to improve their times.

The duo clocked 58 laps between them in a smooth session for the world champion outfit, but it was not so positive for rival Ferrari and McLaren.

Championship leader Sebastian Vettel stopped at the exit of the pitlane, reporting an issue with the gearbox with just over an hour to go.

After a short spell in the garage, the German rejoined the fray and ended up fourth quickest, just over a tenth adrift of his team-mate.

Fernando Alonso's session lasted just a handful of corners, his car snapping approaching Turn 3 with smoke and fluid pouring from his Honda power unit.

Honda said it was an oil leak and in a bid to ensure he gets out for second practice, chose to change the engine while it investigated the problem.

Alonso's team-mate Stoffel Vandoorne had a more fruitful session, recording 24 laps and the 12th quickest time.

Max Verstappen was the best of the Red Bulls in fifth, 1.185s off the pace and four tenths clear of team-mate Daniel Ricciardo.

Kevin Magnussen beat Romain Grosjean to seventh, but his session ended a few minutes early when he parked the Haas at the edge of the track at Turn 4.

Renault's Nico Hulkenberg and Toro Rosso's Carlos Sainz Jr completed the top 10.

Sergey Sirotkin, who took over Jolyon Palmer's Renault for this session, managed 10 laps and the 19th quickest time before his outing was curtailed by a water leak.

PRACTICE ONE RESULTS: