Liam Johnston produced the lowest round of his European Tour career on Thursday, firing a sparkling 61 to lead by a single shot at the end of the first day of the 2020 Portugal Masters.
After notching four early birdies to reach the turn in 31 blows, the Scot put himself in a strong position to match the historic 59 Oliver Fisher shot here two years ago, with further gains at the tenth, 12th, 13th, 15th and 16th taking him to nine under par with the long 17th still to come.
He narrowly cleared the water with his approach into Dom Pedro Victoria Golf Course's final par five but could not hole his eagle putt from range.
Johnston went for the pin with his second shot at the 18th in a last ditch attempt to tie Fisher's European Tour record but had to settle for a par at the last to head into the clubhouse on ten under par.
Afternoon starter Julien Guerrier made nine birdies - including four in a row from the 14th - in his flawless 62 to sit alone in second on nine under.
England's Laurie Canter was two strokes further back on seven under after making seven birdies and no bogeys.
Johnston made a strong start on Thursday morning, picking up a shot at the first before reeling off a hat-trick of birdies at the fourth, fifth and sixth to get to four under.
After starting his back nine with another birdie on the tenth, the Dumfries native took advantage of the par five 12th before holing his 18 foot birdie putt at the 13th to join early clubhouse leader Canter on seven under.
He left his 12 foot birdie try short at the 14th but got up and down from the rough for another gain on the 15th to grab the outright lead.
Johnston sent his tee shot at the par three 16th to around 20 feet before nonchalantly knocking that in for yet another birdie.
The 27-year-old's heart must have been in his mouth at the long 17th when his approach only just cleared the water and landed safely on the green.
He could not make his lengthy eagle putt there but tapped in for a birdie, knowing he would now need to hole his second shot at the 18th to make a 59.
Johnston was unable to do that, lifting his approach past the pin and into the first cut of rough behind the green.
He left his chip four feet short of the hole but rolled in his par putt to sign for a bogey free 61.
"With the rough out there, it's nice to keep the bogeys off the card," said Johnston, whose best finish of the season so far is tied 15th at the ISPS HANDA Wales Open. "I saved well when I needed to and I holed a lot of good putts out there. I'm delighted with the ten birdies.
"I told my coach back home that I was swinging it as good as I have. My game feels like it's really trending in the right direction, more importantly I'm in a really good place mentally.
"I didn't see a round like this coming but I feel like I was playing well."
Guerrier followed up a birdie at the first with further gains on the fourth, fifth and eighth to head to the turn in 31.
After picking up another shot on the tenth, the Frenchman charged home with birdies at the 14th, 15th, 16th and 17th before parring the last to sit one stroke behind first round leader Johnston.
Guerrier said: "I really enjoyed how I played the course today. The conditions were great, the weather was perfect.
"To play this course after Valderrama, I think it helped, because Valderrama is like a washing machine.
"I played great, I hit a lot of fairways and I think that is the key here.
"As soon as I hit my ball into the rough it was a different hole, you fight for the par, and when you put your ball on the fairway it's like a birdie chance. You try to make it the best you can.
"Since my injury I have been struggling with my game, so I have worked a lot with my caddie, with my coach and tried to come back."