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.