Marchbank, a former player on the European Tour, went to the turn in 33 with three birdies and just one dropped shot and then came back in 33 with three more birdies.
"I missed qualifying in the regional competition on this course last year," Marchbank said. "But I reckon that 66 will be quite good enough this time."
Marchbank's first birdie came at the second where he chipped to three feet. He three-putted the fourth to drop his only shot of the round but then birdied two in a row with putts of 35ft at the seventh and 15ft at the next.
His inward half was unblemished, his putter again working well for birdies at the 10th with a 15ft putt and the 16th, where he holed a 20 footer. He followed up by chipping to three feet for his final birdie at the 17th.
Another former European Tour player, Phil Harrison, is on course to qualify for the Open for a sixth time. Now director of golf at Aldwark Manor near York, Harrison was first off at Carlisle and made the most of the perfect conditions with a three-under-par 68. Harrison hit 17 greens and the one green he missed - the 18th - was just by three inches, and he holed from 15 feet for his third birdie.
Harrison, who quit the Tour to move into golf design and management, parred the first nine holes and then birdied the 10th and 11th. A wedge to 18 inches at the 383-yard 10th and an eight iron to 12 feet at the 384-yard 11th took him to two under par and a wedge to the back of the 18th gave him his third birdie and a two-shot lead over Buchanan Castle's Jason McCreadie, one of his playing partners.
Sion Bebb, of Mountain Lakes, Caerphilly, set the early pace at Copt Heath with a level-par 71. Two birdies in the opening nine holes enabled Bebb to reach the turn with a one-under 34 but then he suffered a blip, dropping three shots at the 10th, 11th and 12th holes. The Welshman displayed commendable fortitude and kept in contention by firing home another two birdies, at the 540-yard, par-five 15th and the 332-yard, par-four 18th.
Results, Digest, page 27