Matt Wallace saw his lead trimmed by Germany's Sebastian Heisele but remained firmly in control of the Open de Portugal at Morgado Golf Resort midway through the third round.
The 27 year old, promoted to the Challenge Tour after winning six times on the Alps Tour last term, including a run of five successive victories, had retained his five shot overnight advantage when the second round was completed this morning.
Bad weather over the first two days had caused delays, but in brighter conditions in Portimão Wallace picked up a birdie on the ninth, his last, to complete a second round 66.
That gave him a bogey-free halfway total of 17 under par.
Two opening pars saw Wallace take his bogey-free run to 38 holes, but having overcome a bogey on the third with a gain at the next, the Englishman dropped another shot at the sixth.
Wallace birdied the ninth for the third time this week to turn in a level par 36, but birdies at the second and seventh - either side of a bogey on the fifth - saw Heisele move within four.
Home favourite José Filipe Lima, France's Matthieu Pavon and English pair Sam Walker and Ben Evans were a shot further back on 12 under.
A shot further back another Englishman, former European Tour winner Oliver Fisher, had carded a fine 68 to set the clubhouse target at ten under.
"The only tricky thing out there is controlling the ball in the wind," said Fisher. "As long as you are driving it okay, you don’t necessarily need to be hitting fairways, as long as you’re controlling the ball and your distances.
"I had a few nice numbers, hit some decent shots, and putted nicely. It was a good, grinding round.
"I made some nice putts on the front nine. I hit a lovely shot into the eighth and made a par from there. That was probably one of my best shots of the day."