Jonathan Lomas carded a 6-under 66 and is alone in third place at minus-10.
After the 36-hole cut on Friday, the entire field was separated by only five shots, which was a new European Tour record for fewest strokes between first and the cut.
Saturday's third round put some distance between the field and first place but the day was about more than golf. In the middle of the round, there was a minute of silence for the victims of the train bombings in Madrid on Thursday.
Once golf was again the focus, Jacquelin collected five birdies through his first 11 holes to move up the leaderboard. He birdied two of his last three holes to reach 11-under par in the clubhouse.
Jacquelin was denied his first European Tour victory in January when he was defeated by Marcel Siem in a playoff at the dunhill championship. The 29-year- old Frenchman is not forcing the issue when it comes to victory No. 1 on tour.
'I'm not impatient to win,' said Jacquelin. 'I think the way to win is to make sure you are not impatient. Let it happen. I think it will happen and when it does I won't be surprised. Yes, I am going for that win and I had a good chance in the dunhill championship, but I will stick to my same routine and do what I normally do. I won't change anything.'
Sato, who turned 34 on Friday, birdied the fifth then knocked a 5-wood to 15 feet to set up an eagle at the 10th. He birdied 15 and 16 to join Jacquelin in first.
Sato, who earned his tour card through Q-School last year, is also in search of his first title on the European Tour and admitted he will be nervous Sunday morning.
'I am very excited but I will also be pretty nervous,' said Sato, one of five co-leaders after Friday's second round. 'I was quite nervous this morning and I have to keep reminding myself that it's only golf and not a life or death situation. I will try to enjoy it.'
Roger Chapman (66), Brian Davis (68), Joakim Haeggman (68), Anders Hansen (67), David Howell (67), Jose Manuel Lara (68) and Siem (64) share fourth place at 9-under-par 207.
Gregory Havret, one of the second-round leaders, shot a 1-under 71 and fell into a tie for 12th at 7-under par. Former Masters winner and Order of Merit champion Ian Woosnam, who was part of the logjam in first after the cut, managed an even-par 72 to come in tied for 18th at minus-6.
The other two overnight co-leaders did not fare as well. Andrew Oldcorn posted a 1-over 73 and is tied for 28th at 5-under par, followed by Gary Murphy, who struggled to a 2-over 74 and is knotted in 38th at 4-under-par 212.