Swede Joakim Lagergren (70) was in second spot, with Belgium's Thomas Pieters (71) and South African Richard Sterne (67) a further shot back at nine-under.
Dredge, a double winner on the European Tour who has not tasted victory since the 2006 European Masters, reeled off five birdies on his front nine to surge to the top of the leaderboard.
Though he ran up his only bogey of the day at the par-four 13th, the 43-year-old rebounded with a birdie at the 14th before parring his last four holes to remain three strokes clear.
"You come to courses sometimes and it just seems to suit your eye," said Dredge who finished second at this tournament in 2014 and sixth last year.
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"I'm just glad that I'm here and performing," he told reporters. "You try not to think too much about the score but I thought under 70 was going to be a good score out there today.
"It really was blowing, approach shots were tough, putting was very difficult to start with ... obviously I'm delighted with my score. I'm in good position for the weekend."
Englishman Tom Lewis, joint first-round leader with Lagergren and Pieters after opening with a course record 62, carded a 72 to finish the second round at eight-under, level with Spaniard Adrian Otaegui (66).
(Reporting by Mark Lamport-Stokes; Editing by Tony Jimenez)
