Jordan Spieth's made an impressive start to his bid to secure the third leg of a calendar grand slam at The Open Championship.
The American, winner of the first two Majors of the year, quickly moved to five under after seven holes in benign conditions at St Andrews, just one off the lead.
Spieth birdied the first two holes from inside 12 feet, and reached the 570 yard par five fifth in two and two-putted from 45 feet for birdie, with two more birdies following at the sixth and seventh to get to five under.
He left another birdie attempt from 25 feet at the next inches short but looked in ominous form as he approached the turn.
Up ahead Robert Streb topped the leaderboard on six under, just in front of veteran two-time Major winner Retief Goosen who was making the most of coming through a play-off in final qualifying to be five under.
Big-hitting American Dustin Johnson carded the tournament's first eagle after a brilliant approach to the fifth helped him to four under.
England's Greg Owen, out in the first group at 6.32, posted the clubhouse lead on four under after the rarefied atmosphere got the better of debutant David Lingmerth, whose remarkable seven under par outward nine of 29 was followed with three bogeys and a double bogey on the way in as he finished with a three under 69.
Johnson moved to five under after driving to the 332 yard par four ninth, but playing partner Spieth's birdie attempt, set up in more conventional fashion, just brushed the edge of the hole as both turned in 31.
Streb's 12 foot par save at the 17th allowed him to finish with a six under 66 and set the new target.
Johnson then holed from close range to move joint top on six under with eight holes - albeit it the more difficult ones - still to play and almost holed his birdie attempt from the fringe of the 11th green.
Spieth, from a similar position, benefited from the read and sank his putt to join his compatriot at the top.
Both could not capitalise on the 348 yard par four 12th despite Johnson smashing his drive pin-high just right of the green.
American 21 year old Jordan Niebrugge tied the Old Course record for lowest score by an amateur at The Open with a five under 67.
Goosen got to six under, as did 2011 Masters champion Charl Schwartzel and 1999 Open Champion Paul Lawrie to briefly make it a six-way tie at the top.
However, Spieth proved he is human after all with a bogey at 13.
Streb admits he was mildly surprised by his opening round considering his lack of experience of links golf.
"None. Never been over here," he said.
"I felt like I was starting in a pretty good place at St Andrews but never done much with links golf. Robert Streb
"I played a practice round with Tom Watson on Tuesday. He was pretty helpful."
Goosen, playing in his first Open for three years, was happy with his 66, saying: "It's definitely one of the best rounds I've played around here at St Andrews but you know it's a long way to go.
"Maybe there is something good coming."
Not long after, Lawrie birdied the 13th to reach seven under.
