Lucas Herbert stormed into a two-shot lead at the British Open on Friday after the Australian and American Sam Burns equalled the record for the lowest round in major golf history on Friday with eight-under par 62s.
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Bryson DeChambeau had closed to within one shot of Herbert before being hit by a two-stroke penalty for unintentially improving his lie.
World number 97 Herbert doubled over his putter in anguish as a short attempt for par on the 18th slipped by with the chance to become the first man to post a major round of 61.
Burns followed suit less than an hour later after six birdies on the back nine, including a chip on from the bunker on 18, to move to five under for the tournament.
A dramatic second round took another twist after the close of play when two-time US Open champion DeChambeau was penalised for trampling down grass before his second shot at the fifth hole after a lengthy and animated discussion with rules officials.
Under glorious sunshine in Southport on England's north-west coast, Herbert got off to a flying start with birdies on his opening three holes and added three more at the fifth, seventh and ninth to hit the turn in 28, a British Open record for the front nine.
His momentum continued with birdies at the 12th and 13th before a perfect approach set up another three at the par-four 16th for a shot at history.
Despite a wayward tee shot at the last, he should still have scrambled for a par, but the moment in front of huge crowds seemed to get to the 30-year-old as two tentative putts resulted in his first bogey of the day.
"It was not lost on me the amount of history in major championships and the opportunity I had to obviously break the record," said Herbert, who has spent the last two years on the breakaway LIV Tour.
"To tie it as well is still something I'm really proud of."
Burns took the opposite route to 62 with a six-under 30 on the back nine to surge into contention.
The world number 18 sank a 20-foot birdie at the 17th and then chipped in from the greenside at the last for his share of history.
"I caught myself by surprise," said Burns. "I think the finish there the last three holes was just a bonus."
Both players equal the course record set by Branden Grace the last time the British Open was held at Birkdale in 2017, one of five previous rounds of 62 at majors.
MCILROY MAKES THE CUT
World No 4 Cameron Young is well in the running for his first major at six under par, alongside overnight leader Jackson Suber and Ryan Gerard.
Defending champion Scottie Scheffler is four shots back but could easily have been at least in a share of the lead but for a series of missed short putts with birdie opportunities for the world No 1.
Rory McIlroy recovered from a difficult opening round of 72, that included six bogeys, to at least put himself in position to mount a surge up the leaderboard over the weekend
The six-time major champion posted a 67 to move to one under for the tournament.
"I think the main objective today was to be here for the weekend, which I am," said McIlroy. "I think if I can get off to a decent start tomorrow, be four of five under for the tournament, I'll be right in it."
Tommy Fleetwood's late charge was met with deafening roars around his home town with three birdies in the final five holes to get to four under par.
World No 3 Matt Fitzpatrick and Justin Rose were among the big names to miss the cut.