Benn Barham fired a 6-under 65 to vault up 26 spots into a share of third place. Barham joined David Drysdale (69) and Andres Romero (68) at 9-under-par 204.
Defending champion Tim Clark posted a third-round, 2-under 69 and is tied for sixth place with Raphael Jacquelin (65), Damien McGrane (71) and Jean- Francois Remesy (67). The group is knotted at minus-8.
Clarke began the third round with a three-shot lead and collected his first birdie at the fourth when he drained a 7-footer. He added another birdie at the par-5 sixth to move to 13 under par, but trouble loomed.
At the par-4 seventh, Clarke missed the green and chipped to 4 feet. He missed the par putt right and bogeyed the hole to fall to minus-12. Clarke did not have many realistic birdie putts, except for a missed 8-footer at the ninth.
He made seven pars around the turn, but collected some amazing saves. At the 12th, Clarke drove in the rough and came up short with his approach. Clarke chipped to 7 feet and converted the par putt to stay at 12 under par.
Two holes later at the driveable par-4 14th, Clarke found water left of the putting surface. He dropped, hit his third to 6 feet and once again holed a clutch par save.
The clutch putting abandoned Clarke at the 15th. His second came up short of the green and this time Clarke missed a 4-footer that would have kept him at minus-12. Now at 11 under, and tied with Bjorn, Clarke rolled in a breaking, 15-foot birdie putt at 16 to reclaim the outright lead.
That did not last long as Clarke hit another poor iron at the par-3 17th, coming up short of the green. Clarke chipped 15 feet short of the stick and missed the par putt, again falling into a tie for the lead with Bjorn, who was in the clubhouse.
Now it's a battle with his friend and former Ryder Cup teammate Bjorn as Clarke goes for his 11th European Tour victory but his first since the 2003 WGC-NEC Invitational.
'We're very good friends,' said Clarke. 'I would certainly like to be four or five shots ahead of him as I could have been as opposed to tied for the lead, but we'll have some fun.'
The Dane tallied three birdies in his first six holes, but bogeyed the seventh, a hole he has made five on in each of the first three rounds of the tournament.
Bjorn recovered with a birdie at nine, a hole he has birdied each of the first three rounds. He parred the first three holes on the second nine, then birdied No. 13.
Bjorn, who won this year's Irish Open, recorded pars on his next four holes, then ran home an 8-foot birdie putt at the closing hole to get in at minus-11.
Now Bjorn has a shot to win at the same venue as his first win on the European Tour.
'It has got a huge place in my heart and always will have,' said Bjorn, who has nine wins on tour. 'Any pro will tell you their first victory is the most special one. I don't think we play a finer venue on the tour. When it is like this and the weather is fine, it is spectacular.'
Ernie Els, a two-time winner of this tournament, shot a 4-under 67 on Saturday. He is tied for 10th place with Jamie Donaldson (71), Mark Foster (68) and Charl Schwartzel (72). The group is knotted at 7-under-par 206.