SANDWICH, England (Reuters) -With a clear blue sky above, the lightest of breezes and fairways still playing relatively soft, the Royal St Georges's course looked vulnerable when Scotland's Robert Macintyre fired six birdies in his third-round 65 on Saturday.
His five-under round rocketed him up the British Open leaderboard, and with 10 other players in the early groups going sub-par a day of low scoring looked on the cards.
There is a usually a sting in the tail of any classic links course, however, and despite the tranquil weather some teasing pin placements meant the scoring was kept under control.
Only one hole on the front nine, the seventh, was playing under par midway through the third day, although former Open champion Rory McIlroy found five birdies before the turn as he looked to play his way back up the leaderboard after consecutive even-par 70s.
But the course bit back as a poor tee shot at the 10th cost him a bogey and two more followed on the 13th and 15th to leave the former world number one at one under for the tournament, 11 behind leader Louis Oosthuizen of South Africa.
"The back nine played tough. They're sort of tucking the pins away. They've stretched the golf course out to as long as it can play," McIlroy told reporters.
Macintyre stayed out of trouble to rack up six birdies in what turned out to be the best round of the day with leading trio Oosthuizen, Collin Morikawa and Jordan Spieth only a combined four under par for their third rounds.
Oosthuizen had shot 64 and 65 in his opening two rounds -- the 129 total being the lowest after 36 holes in Open history.
Considering the benign conditions it was surprising to see the course yield only 24 sub-par rounds on Saturday although the R&A, according to Oosthuizen, had set the pins in "very questionable" positions.
Spain's U.S. Open champion Jon Rahm agreed after he shot a two-under 68 to move to seven-under.
"Maybe some of the hardest pin positions I have ever seen," he said. "You cannot tell on TV but they are almost always on top of a little hill. It's a way of defending the golf course."
(Reporting by Martyn Herman; Editing by Hugh Lawson and Ken Ferris)