Karlsson recorded six birdies on The Marquess Course at Woburn Golf and Country Club. His 6-under-par 66 was good enough to give the 31-year-old Swede a one-shot advantage over Australian Adam Scott, who also has a victory under his belt this season.
Colin Montgomerie, winless in 2001, opened in 4-under-par 68. Hes tied with several others for third place.
Montgomerie was 3-over through his first four holes in the first round, but recovered with an inward half of 30.
To come back in 30 was good because it proves there is not a lot wrong with my game and to hole a 50-footer at the last was an added bonus, said Montgomerie.
I havent won on the European Tour for over a year and that is becoming a bit of a problem, he added. I need to win and I like this course ' certainly one of the best layouts weve played this year.
Karlsson, too, praised the new venue.
Its a beautiful golf course, Karlsson said. I think they have done a very good job on the design. It is one of the top new courses I have played.
Scott, who won the Alfred Dunhill Championship in January, birdied his final three holes to end his round of 67. Ironically, he played in the same group with Justin Rose, the man he beat in South Africa.
I really enjoy playing with Justin, said Scott. We get along great and actually had dinner together last night in Woburn and just hung out a little bit together.
Rose carded a 2-under-par 70.
Lee Westwood is three off the lead after a 3-under-par 69. The Englishman decided to play this event after missing the cut last week in the Volvo PGA Championship.
Full-field scores from the Victor Chandler British Masters