Nico Rosberg romped to an effortless victory at the Spanish Grand Prix while Lewis Hamilton was frustrated by Sebastian Vettel for much of the race.
At a race-track where overtaking is notoriously difficult, pole-sitter Rosberg made a speedy start to pull away by a second at the end of lap 1.
That advantage was ahead of Vettel as the Ferrari driver nipped past Hamilton at the start and instead of fighting back, the World Champion was forced to defend against Valtteri Bottas.
Running third behind Vettel, Hamilton was the first of the leaders to pit in a move designed to undercut the German. "Do the opposite to Vettel," he was told and dived into the pits just as his rival past the entry road.
But instead of undercutting him, a slow pit stop – Hamilton was stationary for 5.3s due to a minor problem on his rear left – meant that when Vettel pitted a lap later, the German came out with his advantage up to three seconds.
Rosberg pitted after the battling pairing and easily emerged back in the lead when all the stops played out, some seven seconds up the road from Vettel.
Although Hamilton closed right up on Vettel, the gap down to two-tenths at some stages, he conceded it was "impossible" to pass out on track and had to fall back to preserve his tyres.
Hamilton was again the first of the leaders to stop, in on lap 33 as he opted for Plan B, a three-stop strategy. Vettel only came in lap 41 with Hamilton again in on lap 51. His third stop allowed the Brit to swoop into second ahead of Vettel while on fresher rubber he easily pull away from the Ferrari driver.
While that pairing battled it out over second, Rosberg, who stopped for the second time on 45, drove unchallenged to the chequered flag, claiming a comfortable first win of this season.
The 25 points meant the German also cut into Hamilton's lead in the Drivers' standings which is now down to 20 points after five races. Vettel's P3 on the day ensured he stayed third on the log.
Valtteri Bottas held off the charging Kimi Raikkonen, who went medium-hard-medium, to finish fourth ahead of his compatriot while Felipe Massa was sixth. The Williams driver was the last time not to be lapped by Rosberg.
Daniel Ricciardo was seventh for Red Bull Racing but was once again a full lap down on the race winner.
He beat Romain Grosjean while Carlos Sainz crossed the line in ninth place after a last lap battle with Daniil Kvyat in which the duo touched and Sainz ran wide.
Fernando Alonso was the afternoon's first retirement much to the disappointment of the Spanish crowd.
He had been running as high as seventh place before he pitted, the last driver to do so, and returning to the action down in 14th place. However, it was evident shortly after that he had brake problems as he ran off the track at Turn 1.
Back in the pits, Alonso was not able to stop on the mark and overshot his box before his mechanics pulled him into the garage and the Spaniard retired from his home race.
Pastor Maldonado, driving with a broken rear wing for much of the race after an early incident with his team-mate, retired on lap 47.
1 Nico Rosberg Mercedes 1:41.12.555
2 Lewis Hamilton Mercedes 17.5
3 Sebastian Vettel Ferrari 45.3
4 Valtteri Bottas Williams 58.4
5 Kimi Raikkonen Ferrari 59.2
6 Felipe Massa Williams 80.3
7 Daniel Ricciardo Red Bull 1 LAP
8 Romain Grosjean Lotus 1 LAP
9 Daniil Kvyat Red Bull 1 LAP
10 Carlos Sainz Toro Rosso 1 LAP
11 Max Verstappen Toro Rosso 1 LAP
12 Felipe Nasr Sauber 1 LAP
13 Sergio Perez Force India 1 LAP
14 Marcus Ericsson Sauber 1 LAP
15 Nico Hulkenberg Force India 1 LAP
16 Jenson Button McLaren 1 LAP
17 Will Stevens Manor 3 LAPS
18 Roberto Merhi Manor 4 LAPS
Did Not Finish
Pastor Maldonado Lotus 21 LAPS
Fernando Alonso McLaren 40 LAPS