South African Louis Oosthuizen defied the wildly fluctuating weather to move into the lead on the second day of The Open Championship at St Andrews.
Northern Ireland's Rory McIlroy carded a stunning opening 63, nine under par, to equal the lowest round ever in a Major Championship, but Oosthuizen was only two behind overnight following an excellent 65 compiled despite tougher conditions.
Oosthuizen was in the second group out today at 6:41am and initially looked set to benefit from similar weather which Thursday's early starters had turned to their advantage.
But a heavy shower arrived after three regulation pars, although that did not stop the 27 year old from eventually carding his first birdie of the day on the 568 yard par five fifth, chipping to three feet after almost reaching the green in two.
Another birdie promptly followed from a similar distance on the next, and when he made it three in a row from ten feet on the seventh - the rain having stopped - Oosthuizen took over the lead on ten under par.
After reaching the turn in 33, Oosthuizen drove the green on the 386 yard par four tenth and two-putted for his fourth birdie of the day.
Coming up short of the green on the par three 11th cost him a first bogey of the day, but a well controlled pitch to three feet on the 12th helped restore his two shot cushion.
American Ricky Barnes was up into outright third on eight under par after birdies on the first and seventh and an eagle on the fifth, while 1989 champion Mark Calcavecchia was six under after picking up four shots today.
England's Paul Casey, reportedly suffering from a bad chest infection, had nevertheless started with three straight birdies to move to six under par, but missed out on a fourth when he three putted the par five fifth for par.
McIlroy, at 21 looking to become the youngest winner of The Open Championship since Willie Auchterlonie in 1893, was not due to start his second round until 1:31pm, but World Number Three Lee Westwood had opened with four pars.
Westwood, who has been struggling with a torn calf muscle, carded an opening 67 despite arguably having the worst of the conditions in the afternoon.
Oosthuizen dropped his second shot of the day by three-putting from long range on the 13th, but immediately restored his two shot cushion with a birdie on the par five 14th.
The Old Course was bathed in sunshine as Calcavecchia birdied the 18th to complete a flawless 67 for a halfway total of 137, seven under par.
By way of comparison, Tiger Woods was 11 under par after 36 holes on each of the two occasions he has lifted The Claret Jug at St Andrews, in 2000 and 2005.
