By Rob Hodgetts
BBC Sport at St Andrews
Tiger Woods stamped his authority on the 134th Open with a first-round 66 to lead by one stroke at St Andrews.
Woods scorched to six under early on and seemed untouchable until Australian Mark Hensby emerged from a deluge to card a 67 in the evening sunshine.
England's Luke Donald and South African Retief Goosen were in a gaggle of players one stroke further back.
Jack Nicklaus, the 18-time major champion, carded a three-over 75 as he bids to make the cut in his final Open.
Hensby, who tied third at the US Open and fifth at the Masters, ignited his round with an eagle at the par-four ninth to go two under before charging to five under after 15.
The 34-year-old had a chance to join Woods as overnight leader after almost driving the green on the 18th, but he took three to get down.
Hensby, playing his first Open, said: "No-one expects me to win. The bottom line is if Tiger or Vijay, or the big-hitters are on, you really don't have a chance.
"I'll just go out and play on Friday, but I don't dwell on any expectations."
The only other challenger to the world number one was Spain's Sergio Garcia, who reached five under after 12 holes but stumbled during the afternoon showers and ended on 70.
"Finishing at six is a great start to the tournament," said Woods, 29, who won by eight shots the last time the Open was held on the Old Course in 2000.
Also on 68 were the likes of Fred Couples, Scottish amateur Eric Ramsay, 25, the Australian amateur champion, and Spain's two-time Masters champion Jose Maria Olazabal.
Another stroke adrift was a group which included US Open winner Michael Campbell, world number two Vijay Singh, England's Simon Khan, Northern Ireland's Graeme McDowell and Frenchman Thomas Levet.
England's Ian Poulter and Simon Dyson and Ireland's Paul McGinley all ended with rounds of 70, while home favourite Colin Montgomerie shot 71.
Defending champion Todd Hamilton was in esteemed company at two over alongside 2002 winner Ernie Els, American world number four Phil Mickelson and England's Nick Faldo, a three-time Open champion.
The players and a crowd of 38,000 paused to observe a two-minute silence at 1200 BST to remember the victims of last week's London bombings.
Woods, aiming for his 10th major title and second Open, started at 0820 BST in chilly but calm conditions and cruised through three holes in level par before putting his foot down with birdies at the fourth, fifth, seventh and ninth to go out in 32.
His birdie at the par-four seventh, the beginning of the famous St Andrews loop, where good rounds are often built, came via the vast and cavernous Shell bunker.
It was the American's first visit to the sand in over four competitive rounds at St Andrews, including the entire 2000 tournament.
A further surge took Woods to seven under after 12 to establish a three-shot lead as he threatened to end the event as a contest halfway through day one.
But dropped shots on 13 and 16, after finding pot bunkers off the tee, narrowed the gap before a final flourish and a three on the last in front of the R&A clubhouse.
The American's charge eclipsed the stirring early effort of rising star Donald, who came third on his Masters debut in April.
The 27-year-old ignored the pressure of playing with Nicklaus and his old sparring partner Tom Watson (75) to craft an impressive 68, marred only by a bogey on the short 11th.
"The atmosphere was amazing and it was nice to play some good golf for the crowds," said Donald.
"It's a solid start, no more. There were some tough pins but there were still birdies to be had because the wind wasn't nearly as fierce as it can be.
"If I shoot another three 68s I might be close. But you can't worry about what Tiger or anyone else is doing."