Masters champion Danny Willett maintained his perfect start to the BMW PGA Championship in the early stages of the second round at Wentworth.
In his first round in England since winning his maiden major title at Augusta, Willett carded a flawless opening 66 to lie just a shot behind joint leaders YE Yang, Joost Luiten and Scott Hend.
And although he initially had to work hard to remain blemish-free on Friday, a hat-trick of birdies from the third took the world number nine into the outright lead on nine under par.
Willett saved par from seven feet on the first after firing his approach over the green and also had to hole from similar distance on the second after charging his birdie attempt past the hole.
The 28-year-old then holed from 10 feet for birdie on the third and picked up another shot on the downhill par-five fourth, which played the easiest hole on the course in the first round, before making it three in a row on the next.
That took Willett a shot ahead of stablemate Luiten, who had birdied the second, with Hend and former US PGA champion Yang among the later starters.
Willett, whose previous best finish at Wentworth was fifth on his debut in 2010, showed no signs of easing up and made it four birdies in a row when his approach to the sixth span back to within four feet of the hole.
Another brilliant iron shot to the eighth set up his fifth gain of the day from a similar distance and, when he holed from 10 feet on the ninth, the 28-year-old had reached the turn in just 29 shots.
At 12 under par he was five clear of Luiten and on target to smash the tournament record for the lowest opening 36 holes set at 13 under in 2008 by Paul McGinley, who had earlier been forced to withdraw from the second round with a back injury.