Paul Dunne took a two-shot lead into the back nine as the third round of the Open de España moved towards its conclusion at Centro Nacional de Golf.
The Irishman entered the day three ahead but saw that lead trimmed to one with four opening pars as the chasing pack made birdies in more ideal scoring conditions in Madrid.
Dunne responded with a hat-trick of birdies to turn in 33 and move to 16 under, two shots clear of World Number Four Jon Rahm and Swede Henric Sturehed.
Andy Sullivan fired a brilliant 65 to set the clubhouse target at 13 under and sit a shot clear of fellow Englishmen Aaron Rai and Callum Shinkwin, home favourite Nacho Elvira and Australian Brett Rumford.
Sullivan recovered from an opening 75 with a 63 on Friday and continued to make progress through the field, birdieing the second, third, fifth and ninth with a bogey on the fourth to turn in 33 and move to nine under.
Home hero Rahm played a lovely chip into the first and an approach to tap-in range on the second to get within two of the leader but he was soon leapfrogged by Elvira who also made a birdie-birdie start.
The 31 year old played the par five first in textbook fashion and the holed from nearly 30 feet on the second but he surrendered a bogey on the fourth to drop back to 11 under.
Rahm missed two good birdie chances but he holed an 18-footer on the sixth to get within one of the lead where he was joined by Sullivan after birdies on the tenth, 12th and 13th.
Sturehed had made a birdie-bogey start but further gains followed on the third and fifth and when he spun his approach to the seventh to tap-in range, he was 12 under.
Dunne had made a quiet start but he got up and down from a bunker on the fifth for a first birdie of the day and a two-shot lead, with Elvira also making a gain on the par five.
Shinkwin had birdied the second but made four pars in a row before holing from the fringe on the seventh to join the group two back.
That was soon three as Dunne put his tee-shot on the par three sixth to five feet and his lead was back to where it had been at the start of the day.
Sturehed cut the gap with a brilliant chip-in birdie on the ninth to turn in 32 but Dunne hit straight back, recovering from a poor approach to the seventh with a 35-foot birdie putt.
Rahm played a beautiful bunker shot on the tenth to join Sturehed and when he hit a wonderful approach into the 11th, the gap was down to two once more.
Sturehed would not be left behind, however, and despite finding a nasty spot on the 11th he got up and down with a lengthy putt for another birdie.
Dunne was in a nasty spot of his own on the ninth but he made a brilliant par-saving putt from the fringe to stay two ahead at the turn, with Sullivan taking advantage of the par five last to set the mark.
Rumford had birdies on the fourth and tenth to sit four shots off the lead.
Rai had quietly gone about his business and he added birdies on the fourth, 13th, 15th and last to an eagle on the fifth to sign for a 66.
Jacques Kruyswijk fired eight birdies in his first ten holes - including six in a row from the first - to get to 13 under par and grab a share of the lead before Dunne had even teed off.
Talk of a 59 was quelled by a bogey on the 11th - although preferred lies would have kept Kruyswijk out of the history books - and he double-bogeyed the 17th before bouncing back with a birdie on the last to get to 11 under, alongside Jorge Campillo who had two holes to play.
