And Richie Ramsay was two shots behind after a superb 64.
England’s Graeme Storm held a handsome advantage over a cluster of rivals at 14-under during the round but let his five-shot advantage leak away and is level with Jamieson and Spaniards Pablo Larrazabal and Gonzalo Fernandez-Castano.
Storm, 34, had negotiated his first two rounds and the first 12 holes of his third without dropping a shot but back-to-back bogeys after poor tee shots at 13 and 14 began to undo his good work and the field closed in.
The 34-year-old signed for a one-under-par 69 on a day when low scoring was widespread. Larrazabal and Henrik Stenson posted 64s as well as Ramsay.
“I had two bad swings on 13 and 14,” Storm told europeantour.com.
“I had the tournament in the palm of my hand before that, but it should be a good day tomorrow. I’ve only had two bogeys in 54 holes, which is quite impressive.
“It’s difficult leading like I was. I have a lot of things on my mind at the moment with keeping my card, so I’m just looking at getting the best result I can.
“Tomorrow, keeping my card will be in the back of my mind, but I have given myself the chance to win and if I am in there with six holes to go I will go for it.”