John Catlin remained firmly in control as he reached the turn on day three of the Estrella Damm N.A. Andalucia Masters after carding a birdie and eight pars on his front nine.
The American began the day with a two shot lead and did not put a foot wrong over the first nine holes at Real Club Valderrama, keeping his card clean with seven straight pars before a birdie from 12 feet on the eighth took him to four under par.
Catlin, who is looking to secure his maiden European Tour title this week, confidently knocked in his five foot par putt at the ninth to head to the turn in 34 shots.
That left the 29-year-old three shots clear of his nearest challengers Jamie Donaldson and Lorenzo Gagli, who followed up a birdie at the 11th with a brilliant hole-in-one on the 12th to jump to one under.
Catlin made a steady start to his third round, safely parring his opening four holes while those around him dropped shots in blustery conditions.
After tapping in his five foot par putt at the fifth to stay at three under, Catlin saw his advantage reduced to a single shot when Donaldson holed lengthy birdie putts at the fifth and sixth.
But Catlin's patience was rewarded with a first birdie of the day at the eighth before he closed his front nine with a solid par to sit three clear.
Donaldson started the day in a tie for second on one under but dropped a shot at the second to slip back to level par.
Brilliant birdies at the fifth and sixth - from 25 and 40 feet respectively - took Donaldson to two under but he dropped another shot on the seventh.
Italian Gagli turned in 36 after carding a single bogey and eight pars on his front nine but his round came to life on the back nine as he birdied the 11th and holed his tee shot with a 4 iron from 203 yards for an eagle at the 12th to jump into contention.