Former British Open champion Louis Oosthuizen grabbed an early one-shot lead on a day of high drama and tumultuous swings of fortune in the opening round of the Masters on Thursday.
The South African holed a 20-foot birdie putt at the tricky par-four last for a four-under-par 68 while British world number one Luke Donald was being investigated by tournament officials over suggestions he had signed for the wrong score.
While Donald's plight was in the balance, 2010 British Open champion Oosthuizen was delighted to take control of the year's opening major with four birdies in the last five holes.
Oosthuizen tamed the tricky 18th in the opening round but the hole took a brutal toll on the players as Tiger Woods and Henrik Stenson both came unstuck there.
Tournament favourite Woods bogeyed the hole after driving well left into the pine trees and Swede Stenson, who had led the field by two shots standing on the 18th tee, wound up with an ugly quadruple-bogey eight.
Woods finished with a level-par 72 to lie four strokes behind Oosthuizen, and three adrift of Britain's Paul Lawrie, Spaniard Miguel Angel Jimenez, Italy's Francesco Molinari and American Ben Crane.
Stenson, who had eagled the second and eighth to briefly lead the field by two, returned a 71.
Heavy rain on the eve of the tournament had softened the severely contoured layout and organisers, in response, set up several very tough pin positions to give the course extra bite for the first round.
US Open champion Rory McIlroy, who squandered a four-shot lead going into the final round here last year, was one over after 13 holes and three-times Masters winner Phil Mickelson was four over after 12.
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