David Lynn climbed into second place at 10-under-par 134 after firing a 6-under 66 in the second round. Nick Faldo is one stroke behind him at 9-under-par 135. Miguel Angel Jimenez also posted a 66 and shares fourth place with David Smail and Simon Yates at minus-8.
Bjorn began his round on the 10th tee at Alpine Golf and Country Club. He birdied that hole and came back to birdie No. 12 to get to minus-10.
The 32-year-old stretched his lead with a birdie at the 14th, but stumbled to a bogey at the par-5 17th. The Dane came right back with a birdie at the next to get back to 11 under.
Bjorn birdied the first and third to climb to 13 under and a five-stroke advantage. Despite another stumble, he coasted to the house. He dropped a stroke at the par-5 seventh to drop back to 12 under.
'I said yesterday that when you haven't played for a while you are going to hit a couple of loose shots,' Bjorn said. 'Today they cost me dearly on two par-5s.'
He parred his final two holes to maintain his cushion.
'Hitting a lot of good golf shots is really the key and I'm happy on that score,' said Bjorn, a two-time Ryder Cupper. 'I am happy with my performance in general over the first two days. I thought I kept focused and maintained a good balance in my golf game. You can't ask for more. I am in a good position.'
Lynn began his day four shots behind Bjorn. The Englishman was steady throughout his round though. He birdied the second and the par-3 sixth to get to 6 under.
Around the turn, Lynn birdied No. 10, a hole he bogeyed a day earlier. He continued to make his move with back-to-back birdies from the 14th. Lynn capped his bogey-free round with a birdie on the 17th.
'A couple of years ago, I was trying to win all the time and if I didn't have a chance I basically wasn't interested,' said Lynn. 'This year, coming out on tour, I am playing my own game and trying as hard as I can all the time.'
Richard Green tied for the best round of the day as he carded an 8-under 64. He jumped into a tie for seventh place at 7-under-par 137.
He was joined there by defending champion Ernie Els, as well as Christian Cevaer, Simon Dyson, Scott Gardiner, Anders Hansen, Soren Kjeldsen, Jarrod Moseley and Nick O'Hern.
'I played a lot better today,' said Els, who shot a 5-under 67. 'I hit 13 fairways compared to five yesterday and that's better. I'm getting close. My swing is feeling a lot better and I felt quite comfortable on the greens. It was a good day.'
The cut line fell at 2-under-par 142. Lee Westwood and Jean Van De Velde survived on the number, as 77 players made the cut.
Marcel Siem, who won last week's dunhill championship, finished at minus-1 and Ian Woosnam, even-par 144, were among those who missed the cut.