Closing in fast on Lee Westwood at the top of Europe's Order of Merit - a pounds 250,000 deficit six weeks ago is down to pounds 42,600 - the 30-year-old Ulsterman shot a seven-under-par 64 for a one-stroke lead over Sweden's Patrik Sjoland.
Westwood, back from his hip injury, managed only a 70, as did a disconsolate Colin Montgomerie and Justin Rose, while Nick Faldo's return to form on his return from America is still awaited after a 71.
Clarke opened with a drive and five-iron to within 12 inches of the flag for an eagle and by the time he reached the 15th hole was four under. A perfect drive gave him hopes of another eagle, but what followed had him in fits of laughter with his playing partner Sam Torrance.
"It was a thing of beauty," he said. "I tried to hit a high four-iron, but instead hit it low and fat, 100 yards left into a bunker. Sam had just topped a seven-wood, so we both had a bit of a laugh."
From the bunker Clarke picked the ball out beautifully, hit the flag, and was unlucky that it did not drop for an eagle.
Since missing the cut at the Open Clarke has finished second, second, fourth and 13th. He is on a bit of a roll.
The tournament is the first qualifying event for next year's Ryder Cup, but the man who made his debut at Valderrama last September said: "That's not on my mind at the moment."Reuse content