Lewis Hamilton may have topped both free practice sessions on the opening day of the Canadian Grand Prix, but he warned that he didn't expect to remain there as the weekend unfolded.

The Briton was consistently fastest through the two 90-minute sessions that made up the opening day at the Circuit Gilles Villeneuve but, in edging Sebastian Vettel by a tenth first time around and then Fernando Alonso by 0.05 in FP2, admits that the opposition is in the hunt to deny him another success at one of his most productive venues.

"I'm very happy with my start to the weekend - happy that the rain held off for both sessions today and happy that we got through a lot of good set-up changes," Hamilton, who claimed his maiden F1 win in Canada, commented, "Even though the option tyre was a little quicker, I preferred running on the prime tyre. Today has been positive, but it's definitely going to be tight this weekend - not just for qualifying, but for the race, too."

While McLaren team-mate Jenson Button struggled for track time as his mechanics twice had to change his gearbox, Hamilton admitted that his ability to run two full sessions would stand him in good stead for the rest of the weekend, and was confident that his own talent would help him remain at the front of the pack.

"This is a place where it's important to do some running, because there are some pretty close walls and you need to build your speed up gradually," he explained, "It was an unfortunate day for Jenson, [so] I was very pleased for him that he was at least able to get out at the end of the session and get some laps under his belt.

"This is a great track to drive - a place that requires 100 per cent commitment and where the driver can really make a difference. It magnifies the differences between drivers."

Team principal Martin Whitmarsh confirmed the reasons for Hamilton's confidence, and said that he expected the 2008 world champion to be a factor.

"Lewis is always super-competitive here - he won this race in both 2007 and 2010 - and I'm sure he'll approach tomorrow's qualifying session with his customary confidence again this year," he noted, "He performed extremely well today. His short-run pace was strong, and his long-run pace was excellent."