Australian Nick O'Hern changed his European Tour putting fortunes to catch Ian Poulter for a share of the Wales Open lead as both equalled the Celtic Manor course record 65.
Poulter, despite suffering another bout of tonsillitis, set the seven-under-par target which O'Hern matched in the early evening, leaving them a stroke ahead of Jonathan Lomas.
Europe's 2000 rookie of the year, Poulter at last found his game after a swing-change with coach David Leadbetter, setting the target with eight birdies but bogeying the 14th to deny himself a place on top on his own.
Then O'Hern, who has finished fifth and eighth the previous two times he has played the event, single-putted the first six greens and had his best putting show of the year in compiling seven birdies on an unblemished card to haul into a tie on top.
"Single-putting the first six greens kind of helped my card, which is what I haven't been doing lately," said O'Hern, who bettered his career-best finish by a place when he took second in the co-sanctioned ANZ Championship in Sydney in February.
Poulter is looking for his fourth title and is relieved to be over a poor spell in which he has missed five of the last six cuts after undergoing a swing change with Leadbetter for more consistency in his game.
Having no expectations this week because he was feeling so ill contributed to his setting the pace at the 2010 Ryder Cup venue.
"I felt lousy after playing in the pro-am on Wednesday," said Poulter, "but I dosed myself up with antibiotics. "I won the Moroccan Open with tonsillitis two years ago.
"Today I wanted to just make sure I got around the course and maybe it was a blessing in disguise because I was only trying to swing at 80 percent."
Tournament favourite Colin Montgomerie did not live up to expectations when he carded an indifferent 73 to lie eight strokes off the pace.
Paul McGinley, the 2001 champion, was expected to head the six-strong Irish challenge but once again struggled with indifferent form and last year's Ryder Cup limped home with a 75 on his card.
Instead, it was left to impressive Tour newcomer Peter Lawrie (-4) and Gary Murphy (-3) to challenge the leaders and both are well placed to challenge in tomorrow's second round.
Graeme McDowell started poorly with bogeys on his opening two holes but rallied late in his round to finish with a two under par 70.
Damian McGrane, fresh off a successful defence of his Wexford pro-am title 24 hours ago, made a blistering start before coming back down to earth. He began with three birdies in his opening five holes but a bogey at the sixth followed by a double at the next put paid to his good early work.
From there he steadied the ship and can be pleased with his 72.