Sky's the limit for Lewis Hamilton, says Sir Jackie Stewart

Sir Jackie Stewart fully expects Lewis Hamilton to surpass his tally of three world championships, currently the most won by any British driver, and says there is no limit on what the Mercedes man can achieve.

Hamilton is aiming to become the first British driver to successfully defend a world championship this season, after claiming his second title in 2014. Stewart, who won championships in 1969, 1971 and 1973, is sure Hamilton has plenty of titles to come.

"I won't be upset if Lewis equals my three world championships and I'm sure he'll win more than that," Stewart said. "There will always be somebody leading the pack and the sky is the limit [for Hamilton]."

Stewart also spoke of the cancellation of this season's German Grand Prix, calling it one of the "essential" traditional F1 venues which should always have a place on the calendar.

"That sounds like me being a purist. But you have to respect history. They should always be on the calendar - it's terrific we have a United States Grand Prix, a Brazilian Grand Prix, one in Bahrain, and that we are going to new countries. But you still have to respect your heritage."