Korea's Inbee Park celebrated her 26th birthday by taking the lead in the Ricoh Women's British Open on Saturday, but only after Sun-Ju Ahn was penalised two shots on the 18th hole at Royal Birkdale.
Ahn was playing her third shot from a greenside bunker when television crews reported that she had used her feet to move sand down the side of the bunker, effectively 'building a stance' in violation of rule 13-3.
That meant a par five became a double-bogey seven for a round of 71 which left Ahn alongside Suzann Pettersen and Shanshan Feng on three under par - one behind Park.
"It's disappointing, but it's my mistake," Ahn said. "I still have a day to go and I have to stay focused and try my best tomorrow. I didn't know about the rule but all I was trying to do was make a stance. I'm surprised by it, but if that's the rule, I just have to abide by it and refocus.
"The ball was placed on a very upslope lie, so it was hard to make a stance. So what I was trying to do was fix a stance but after the review it was determined that I used my feet to try to make an even lie.
"My intent wasn't to break the rules. It was just to set my feet firm in the sand just to be able to make the shot. But if that's the rule, there was no intent and I can't do anything about it."
Hull makes her move
Park, who won the first three majors of 2013, carded a 68 on Saturday and said: "The first two days I didn't hit the shots well enough to get the results I wanted but today, my ball-striking was great today and I didn't miss any greens. I am in a great position for tomorrow."
Amelia Lewis and Julieta Granada share fifth place on two under par, with a further seven players, including England's Charley Hull and defending champion Stacy Lewis, a stroke further behind in a tie for seventh place.
Hull's 66 was the best score of the day by two shots and included nine birdies, the 18-year-old bouncing back from a double-bogey seven on the 18th on Friday after hitting her drive out of bounds.
"I can still win it if I have a good day tomorrow," Hull said. "If the wind gets up tomorrow, even par could win it."
Hull was 11 shots off the pace overnight but added: "I said to my dad last night, 'I'm not out of this championship. I think someone was 10 shots off the lead (and won)'."
That was a reference to Paul Lawrie, who was 10 shots behind with just 18 holes to play before winning the 1999 Open at Carnoustie.