America's Michael Allen holds a record five-shot lead after the second round of the US Senior Open, having shot a brilliant 63 at Omaha Country Club.
The 54-year-old went out in 30 after a five-birdie front-nine and then rolled in a long putt for eagle at the par-five 14th to reach seven-under for the day and 10-under for the tournament.
Only eight other players are under par after a hot and breezy day in Nebraska, with Rocco Mediate, who lost a play-off to Tiger Woods for the 2008 U.S. Open, alone in second after a 67 took him to five-under.
His fellow American Jeff Sluman (67) is a shot further back while Tom Lehman and Mark O'Meara, both former major winners, are tied for sixth at two-under.
Kenny Perry followed his opening 67 with a 73 to sit joint 10th at level par, alongside Fred Couples (69) and Tom Watson (70), among others.
Allen clinched his first major title in his debut on the over-50s Champions Tour at the 2009 Senior PGA Championship and has taken control of this event with his lowest score on the U.S. circuit this year.
"It was one of those days," he said. "A few things were really going right for me.
"I am blessed to be able to do this and have an opportunity, especially at this age."
Englishman Roger Chapman won last year's US Senior Open but missed the cut this time after a 76 left him at 10-over.
"I just played rubbish," he said. "I drove the ball terribly. If you can't hit a fairway out here, you can't score. Simple as that."