Henman won the Swiss event in 1998 and 2001

The 30-year-old British second seed, who has been troubled by a magnesium deficiency, was rarely in difficulty against the unpredictable Frenchman.

Twice a winner of this tournament, Henman soon secured the opening set.

He was in control again in the second, maintaining the initiative and sealing the victory in an hour and a quarter.

Henman is now the top remaining seed following home favourite Roger Federer's withdrawal with a thigh injury, and next faces South African Wesley Moodie.

Regarding his health problems he said: "It feels like my energy levels are getting back up.

I'd love to qualify but if I don't I'm not going to let it detract from the great year that I've had. Tim Henman, on the Masters Cup in Houston

"Last week I was really struggling and the doctors could only say that it might be this, or it might not be.

"It has all been a bit strange but I do feel better now."

Henman is currently seventh in the Champions Race, with the top seven qualifying for the lucrative Masters Cup finale in Houston next month.

"If I play like that I have a good chance to qualify," said Henman, who could be overtaken by Andre Agassi or David Nalbandian.

"I'm just going to concentrate on my own performances rather than worry about what everyone else is up to.

"I'd love to qualify but if I don't I'm not going to let it detract from the great year that I've had."

In other first round action, French qualifier Jerome Haehnel toppled Chilean eighth seed Fernando Gonzalez 6-3 6-4.