Ferrari’s Sebastian Vettel won a slow-burning Monaco Grand Prix to extend his championship lead over Mercedes’ Lewis Hamilton to 25 points.
Vettel led home team-mate Kimi Raikkonen after passing the Finn by running longer to their only pit stops.
There was suspicion that the strategy was a deliberate move by Ferrari to get their leading driver into the lead but the team denied that was the case.
Hamilton finished seventh after a difficult race from 13th on the grid.
A largely dull race was enlivened by a late safety car after a collision involving McLaren’s Jenson Button, on his one-off return to F1 in place of Fernando Alonso.
It closed up the field and led to a series of crashes and collisions among the backmarkers.
Raikkonen took his first pole position for nine years on Saturday after Vettel made mistakes on both his quick laps in the top-10 qualifying shootout.
The Finn converted his advantage into a lead at the first corner and the two Ferraris began to edge away from Valtteri Bottas’ Mercedes and the two Red Bulls of Max Verstappen and Daniel Ricciardo.
The race was always going to feature only one pit stop and there was speculation before the race over whether Ferrari would find a way to engineer the strategy to allow Vettel to win.
The way things panned out, it looked as if that was what happened.
Raikkonen made his pit stop on lap 34, at a time when there was no obvious requirement to do so, and he came out behind slower cars, which he had to lap.
Vettel used the opportunity to set a series of flying laps and by the time the German pitted five laps later, he had more than enough of an advantage to rejoin with a two-second lead.
He continued to pull quickly away from Raikkonen, building a 10-second lead within eight laps and cruised to his third win of the year, despite the late safety car period.
Ferrari said Raikkonen’s stop was on the pre-planned lap and that they left Vettel out to avoid the risk of him being passed by Red Bull’s Daniel Ricciardo, who was also delaying his pit stop at the time.
Mercedes knew they would always struggle to make up too much ground with Hamilton after starting 13th because of a messy qualifying session, including a series of driving errors and problems with tyres.
They decided to run him long and hope to gain from his speed once he got some clear air, as cars pulled in to make their pit stops.
Hamilton ran until lap 46 before stopping, by which time he was sixth. He lost only one place, to Toro Rosso’s Carlos Sainz, and ran seventh to the end, closing on the Spaniard but unable to pass him.
“The battle’s not over, boys,” Hamilton said over the radio in the closing laps. “We’ll take these points.”