Tiger Woods lived up to his billing as the red-hot favourite for the 134th British Open, firing a six-under-par 66 to forge one shot clear after Thursday's opening round.
The world number one, champion here in 2000, ended up in three of the 112 bunkers scattered around the Old Course but reeled off seven birdies in nine holes to pave the way for his flying start.
U.S. Masters champion Woods held a two-stroke advantage for most of the day before late starter Mark Hensby of Australia completed a 67 in glorious evening sunshine.
Three-times winner Jack Nicklaus, making his final appearance at St Andrews at the age of 65, produced a few moments of magic on his way to a battling 75 in breezy conditions during the morning.
Americans Nicklaus and Woods joined the other players in pausing during their rounds for two minutes silence in memory of the victims of last week's London bombings.
A run of four consecutive birdies from the par-four ninth put Woods three ahead at seven under but he lost ground with bogeys at 13 and 16, on both occasions ending up in pot bunkers.
He signed off in style, though, chipping to six feet for a birdie at the last and his best start at an Open since he fired a 65 at Royal Birkdale in 1998.
"I feel like I'm playing really well," the U.S. Masters champion told a news conference.
"I've played well in the majors so far, a first and a second is a good start to the year. I want to keep building on it.
GREAT START
"Even though I had it going and was seven under through 12 holes, finishing at six (under) is a great start to the tournament," added the 29-year-old American, who is hunting his 10th career major.
"I made some putts today and that never hurts. I am very happy."
Twice U.S. Open champion Retief Goosen, British Ryder Cup player Luke Donald, Spaniard Jose Maria Olazabal and Americans Fred Couples and Scott Verplank were among a group of 10 tied for third after carding 68s.
World number two Vijay Singh, boosted by an eagle-three at the 14th, moved into early contention with a 69.
Spaniard Sergio Garcia got to five under with six holes to play as light rain swept across the Fife seaside layout in the late afternoon but then slipped back on his way to a 70.
World number three Ernie Els faded after a promising start to return a 74, a score matched by last year's Masters champion Phil Mickelson, who dropped five shots over the last seven holes.
Woods parred the first three holes before rolling in a 20-footer at the par-four fourth and reaching the green in two at the par-five fifth to get to two under.
SPLASHED OUT
Although he was bunkered off the tee at the seventh, he splashed out to six feet for birdie number three. He then holed an eight-footer at the ninth to reach the turn in four-under 32.
At the par-four 10th, he struck his approach to eight feet and calmly sank the putt.
A curling 15-footer followed for birdie at the par-three 11th before Woods stretched his lead to three with an eight-foot birdie putt on 12.
Nicklaus, who made his debut at Royal Troon in 1962, sparked warm applause from a huge gallery when he pitched to eight feet at the opening hole to set up his first birdie.
Although the 'Golden Bear' stumbled at two of the next three holes, he recovered at the par-four seventh where he manufactured a deft bump-and-run from behind a greenside bunker that ended up just five feet from the cup for birdie number two.
Nicklaus, whose last two British Open victories in 1970 and 1978 came at St Andrews, bogeyed 11, 12 and 13 to lose ground before being cheered all the way down the last to complete his round.
"I'm disappointed to shoot a 75 but I probably got what I deserved," said the 18-times major winner. "I'm going to have to shoot four under tomorrow because I don't think par will be good enough to make the cut.
"I'd like to walk across the bridge on Sunday, not on Friday, that's really my goal."