SILVERSTONE, England — Lance Stroll led the second practice for the British Grand Prix on Friday while struggling Ferrari had another bad day, with Sebastian Vettel spending most of it stuck in the team garage.

Stroll finished fourth at the Hungarian GP two weeks ago for Racing Point, which uses Mercedes engines and has been showing good pace this season. Red Bull driver Alexander Albon had the second-fastest time — .09 behind Stroll — but later crashed. Valtteri Bottas was third for Mercedes, ahead of Ferrari's Charles Leclerc and Mercedes teammate Lewis Hamilton.

"There's a lot of heat coming from the cockpit," the championship leader Hamilton said right at the end of a session held amid hot and humid conditions.

Stroll's unexpected teammate Nico Hulkenberg was seventh after filling in at the last minute for Sergio Perez, who tested positive for the coronavirus following a trip back home to Mexico.

Vettel did finally get out on track but was a lowly 18th, about 1.6 seconds slower than Stroll.

Vettel sat out the first session without setting a time because of a problem with the car's intercooling system. Ferrari mechanics stripped the car down to get it ready for the afternoon, but after 30 minutes the four-time F1 champion was back for repairs as the team changed his pedals.

Vettel stood at the back of the garage with his helmet perched on top of his head and a forlorn look on his face. Ferrari is enduring a difficult season, with Vettel picking up only nine points from the first three races with a best finish of sixth in Hungary.

The second session was interrupted half way through when Albon span off the track and slammed backward into the crash barrier. He was unharmed and climbed out. The red flag came out while debris was cleared and the drivers were held up for about 10 minutes.

Time was of the essence for Hulkenberg, who only got the call the day before and was confirmed as the replacement shortly before the session began. The veteran German driver had previously raced for the team when it was known as Force India and adapted quickly.

"He did 45 minutes in the simulator this morning," team principal Otmar Szafnauer said. "He knows the team really well, he knows the engineers."

Szafnauer is not sure if Perez can reclaim his seat for next weekend's race, which is also being held at Silverstone.

"At this point we don't know, we still don't know if England will ask him to quarantine for seven days or 10 days," Szafnauer said, referring to local health and safety protocols.

Verstappen set the fastest time in the first practice and was nearly half a second quicker than Hamilton, although he was on quicker tires than Hamilton, with Stroll third.

There is a third practice on Saturday ahead of qualifying in the afternoon, where Hamilton will aim for a record-extending 91st pole position. The six-time world champion has won the British GP a record six times and is only five wins away from matching Michael Schumacher's F1 record of 91 wins.