David Howell stormed into contention for a first victory in five years at the Irish Open presented by Discover Ireland in Killarney.
The former Ryder Cup star reignited his career with a superb seven under par 64 in the windiest and wettest conditions of the week.
Playing partner Rory McIlroy, the US Open Champion and World Number Four, started with a double bogey and managed only a 72, the same as Graeme McDowell on his 32nd birthday.
The two Northern Irish stars were left deep in the pack on three under while Howell moved alongside German Marcel Siem on 11 under par.
Siem, overnight leader by one and six clear of Howell, still had the back nine to come and he began it with a double-bogey five to leave Howell one in front of fellow Englishman Simon Dyson and Dane Søren Hansen, who had five and seven holes of their third rounds remaining.
Howell reached ninth in the Official World Golf Ranking after he beat Tiger Woods head-to-head in China and then had a runaway victory in the BMW PGA Championship at Wentworth.
But after winning a second Ryder Cup cap later that season his career was blighted by injuries.
The 36 year old stopped the rot when he was close to dropping outside the top 500 and has fought his way back to 282nd.
"I'm flying now - I must be one of the hottest players in the world," he joked.
"I've not been in the best of form, so I was intrigued how I was going to be playing with Rory. He's the star of world golf.
"But there were no nerves and I think I was inspired by the atmosphere. The crowds were amazing."
He also shot 64 on the opening day last year and commented: "They're the best two rounds I've had in a year and three days."
Only once has he scored better in his entire European Tour career.
While McIlroy had two shots on the beach by Lough Leane at the first, Howell parred the first four, then birdied the fifth and seventh to turn in 33 and had five more in a spectacular inward 31 as the weather turned worse.
McIlroy said: "It was not a great start, but I got it together at the end and one over is not too bad considering how I played at the start."
McDowell stated: "I just missed too many fairways and was seriously cold on the greens. They have me seriously confused - I just can't read them at all."
Hansen bogeyed the 12th, but as Dyson reeled off seven pars in a row at the start of the back nine Australian left-hander Richard Green birdied the 15th and joined him in second place, one behind Howell.
Dyson birdied the 17th and Green the last to make it a three-way tie at the top with Howell. Both were round in 67.