McLaren's Lewis Hamilton returned to the scene of his first Formula One victory on Friday and put down an immediate marker with the quickest lap in opening Canadian Grand Prix practice.
The 2008 world champion, a winner in Montreal in 2007 and 2010 but strangely without a triumph in this most unpredictable of seasons, lapped the Circuit Gilles Villeneuve in one minute 15.564 seconds.
Hamilton is a strong favorite to become the seventh different winner in seven races on Sunday and also has his eyes on McLaren's 150th pole.
Red Bull's double world champion Sebastian Vettel was second fastest, 0.118 seconds slower, but ended the morning under investigation for taking a shortcut over the final chicane in overtaking Williams' Bruno Senna.
Germany's Nico Rosberg was third fastest for Mercedes on a grey Montreal morning with Ferrari's Fernando Alonso, the championship leader after six races, fourth and 0.278 off Hamilton's pace.
Australian Mark Webber, winner in Monaco for Red Bull, lapped fifth fastest.
McLaren's Jenson Button, last year's winner after coming from the back of the field at the restart to pass Vettel on the final lap, completed only 12 laps due to an oil leak and was 10th on the timesheets.
The session was red-flagged for 13 minutes when Heikki Kovalainen hit the wall and wrecked his Caterham, spreading debris across the track.
"I was carrying a bit too much speed into that corner. I thought I'd got away with it but the rear end snapped away and that was it," the Finn told the BBC.
"It was just a small error but it happens sometimes. We have got good mechanics. I don't think the chassis was damaged. It's just about replacing the two corners and we go again in the second session."
Compatriot Kimi Raikkonen nearly hit a fox in his Lotus, with the animal darting across the track just before the 2007 champion roared past.
(Writing by Alan Baldwin in London editing by Tony Jimenez)