Hamilton on top in opening practice

SILVERSTONE, England (AP) Formula One leader Nico Rosberg is expected to bounce back and challenge Mercedes teammate Lewis Hamilton at the British Grand Prix thanks to his rival's efforts on his behalf.

Rosberg missed all of the second practice on Friday due to a water leak, while Hamilton clocked the fastest time and completed all the preparatory work for the team.

Hamilton's efforts came just 24 hours after it was announced that the embattled duo, who have collided three times in five races, were given a final warning that they faced fines or suspensions if they crashed again.

Mercedes technical director Paddy Lowe said Rosberg, who was unable to take part, will have the data gathered by Hamilton's work in the session to help him with his car set-up for Saturday's practice and qualifying.

''This isn't great for Nico, this sets him back,'' Lowe said. ''He hasn't had that practice today, but in terms of general homework for the team, Lewis did a fantastic job, running the soft and medium tires in both low and high fuel.

''We've got our data for qualifying, and the race, which will carry across both cars. Nico will benefit from the running from Lewis' car.''

Hamilton was fastest in the second session by three-tenths of a second ahead of Australian Daniel Ricciardo and six-tenths clear of his Red Bull teammate, Dutch teenager Max Verstappen.

''By the time we go into FP3, Nico will get quickly up to speed and tune himself in before qualifying,'' Lowe said. ''You saw how he did it last week in Austria . he has that ability.''

Lowe added that he was uncertain of the cause of the leak.

''We've pulled the car apart,'' he said. ''There's a small water leak and it appeared only just before the session started. We hoped to be able to run through it, without repairing it, because it's a very small leak, but in the end we took the cautious route to protect the engine. There was some risk of damage.''

Rosberg leads the championship from defending champion Hamilton by 11 points.

Sebastian Vettel and fellow Ferrari driver Kimi Rakkonen, who was confirmed as remaining with the Italian team for 2017 earlier in the day, wound up in fourth and fifth places ahead of a resurgent Fernando Alonso.