Lewis Hamilton led George Russell to a Mercedes one-two in Friday practice at the Canadian Grand Prix.

The Mercedes drivers took advantage of setting their fastest times later than the other top drivers to pip early pacesetter Carlos Sainz of Ferrari.

Hamilton was 0.027 seconds quicker than Russell in Montreal.

Aston Martin’s Fernando Alonso was fourth, ahead of Ferrari’s Charles Leclerc and Red Bull’s Max Verstappen, 0.424secs slower than Hamilton.

The day was disrupted by three separate red-flag stoppages over two sessions, and the first session was wrecked by a technical problem with the track closed-circuit television system, which is part of F1’s safety apparatus.

The CCTV problem meant the first session was stopped after only 12 drivers had set just one flying lap and officials decided to extend the second session by half an hour to 90 minutes so teams could make up some of the lost track time.

The revised schedule meant teams ran programmes that differed from each other more than would be usual in second practice.

Mercedes chose to do their race-simulation runs early in the session and their qualifying-style laps later, an unconventional approach.

Red Bull seemed to do their fast laps at the start of the session, when the Circuit Gilles Villeneuve was at its slowest, while Ferrari ran medium-compound tyres at the start of the session before running soft tyres next.

That led to an unexpected order, with Verstappen slower than his usual pace and Mercedes faster.

Alfa Romeo’s Valtteri Bottas was seventh fastest, with the second Red Bull of Sergio Perez, Aston Martin’s Lance Stroll and Alpine’s Pierre Gasly completing the top 10.

The best comparison of pace was provided by the Ferrari and Red Bull drivers, who did their race runs at the same time on the medium tyres.

They provided encouraging numbers for Ferrari – Leclerc was about 0.1secs slower than Verstappen over a run of more than 10 laps. Sainz and Perez were not a match for their team-mates.

Hamilton said: “It was OK. Probably the bumpiest circuit we have been on for a long time. But bit of a strange day. Missed the first session, felt really bad for all the fans.

“I love driving this track. It’s mega. The car didn’t feel bad but I think we definitely have some work to do. Not the greatest but not the worst.

“It is feeling pretty decent but it is just bumpy. I think everyone is having struggles with the bumps. We just have to improve our ride control and a bit of balance through the corner and I think we’ll be all right.

“The car is massively better than last year. The rear end is not but overall it is a step forward and I am definitely feeling the improvements we brought in Monaco.

Russell said: “I don’t think we can read too much into the timings. We did our low-fuel qualifying prep towards the end of the session when the track was quicker. It is bloomin’ bumpy.

“I think we’re still on the tail end (of the teams behind Red Bull), especially on qualifying pace compared to Ferrari and Aston Martin.

“Valtteri looked quick and maybe an Alpine. But we know it comes to us on a Sunday. It looks to be wet tomorrow. We were strong here in qualifying (in the wet) last year. Let’s see what it brings.”

Verstappen said he “didn’t have a good day” and felt the circuit was exposing what few issues Red Bull have with a car that has won every race so far this year.

“We know our limitations with the car,” the world champion said, “and probably with the track like it is now with the bumps and kerbs it is definitely not suiting our package for now but we will try to find a few improvements.”

It was a difficult day for Alpine. Gasly initiated the red flag in the first session when he stopped on track with a lack of drive. The officials then noticed the problem with the CCTV.

And in the second session, his team-mate Esteban Ocon pulled over with a loss of water pressure in his engine.

The other red flag was caused by Nico Hulkenberg’s Haas, which suffered an engine failure on the pit straight.

Rain that had been expected for both sessions held off for most of the day before finally a torrential downpour hit, initially at the hairpin towards the end of the lap, with five minutes to go.

It is expected to be a harbinger of events on Saturday, when the forecast is for heavy rain.