First-round co-leader Phillip Price shot a 2-under 69 and is tied for second with a pair of Englishmen. Ian Poulter (67) and David Howell (64) joined Price at minus-8.
Although Havret played a spectacular round on Friday, the bigger story might be who will not be around on the weekend. The 36-hole cut fell at even-par 142 and some big names in golf will sit out on Saturday and Sunday.
Reigning Masters champion Phil Mickelson shot an even-par 71 and missed the cut by a stroke at plus-1 143. Darren Clarke, one of the favorites for next week's British Open at Royal Troon, only managed a 73 on Friday and came in at 2-over-par 144.
Ben Curtis, whose first title defense comes next week at Troon, finished with three consecutive bogeys for a 1-over 72. He made it through 36 holes at plus-3 145.
But Havret, 27, stole the show on Friday. He tallied four birdies on his front nine, including three in his last four holes.
Havret's second nine started terribly as he parred No. 10, but dropped shots at the 11th and 12th. He rebounded with an eagle at the 13th and birdied three of last four, including back-to-back birdies at 17 and 18.
Havret played in exclusive company on Friday. His playing partners were U.S. Amateur champion Nick Flanagan and 1973 British Open champion and course designer Tom Weiskopf.
And for the last few holes Prince Andrew was an onlooker.
'It has been a beautiful day, to play with Tom Weiskopf and, although I didn't see Prince Andrew, I hear he was watching me play,' said Havret, whose only win on the European Tour came at the 2001 Italian Open. 'Tom is a really nice guy and helped me quite a bit during the rounds. It's a great course and I didn't even know he had designed it before yesterday. It is good to play with one of the legends of the game.'
Price had a 3-foot birdie chance at his last hole, but missed, leaving him in a tie for second.
'I didn't have my 'A' game today but I putted and chipped nicely and got myself out of trouble,' said Price, who shocked the world with a 3-and-2 drubbing of Mickelson in the 2002 Ryder Cup. 'Sometimes you have to do that. I don't think anybody hits it great for all four days and I am pleased with a battling 2 under. I seem to be in a very good frame of mind. I am very patient and doing some good things.'
Poulter began on the second nine Friday and tallied only one birdie on the back side. He birdied three and four for the second time in as many days and reached 8-under with a birdie at No. 7.
At his last hole, Poulter drove into a sand-filled divot. His second landed 8 feet over the hole but he missed the birdie putt. Poulter now has gone through two rounds at Loch Lomond without a bogey.
'It's always good to have a couple of clean scorecards and to roll in a few putts as well,' said Poulter, who is in the hunt for his first Ryder Cup team. 'No mistakes - that's good.'
Howell's last victory on tour came five years ago at the Dubai Desert Classic. The Englishman is starting to get frustrated that a second win has not come yet.
'I suppose I would have imagined I would have won again by now but it hasn't happened,' said Howell. 'Technically I am doing everything better now and my levels have come up tremendously. I am doing everything I can in my life to get that little white ball in the hole in as few strokes as possible. I've just got to keep the faith.'
Tom Lehman, the 1997 winner at Loch Lomond and 1995 British Open champion, carded a 3-under 68 and is tied for fifth place. Thomas Bjorn (67), Christian Cevaer (68), Roger Chapman (66), Kenneth Ferrie (68), Marcus Fraser (68), Peter Hedblom (68) and Tetsuji Hiratsuka (65) joined Lehman at 7-under-par 135.
Eduardo Romero, another of the first-round co-leaders, struggled to a 1-over-par 72 and is part of a group tied for 15th place at minus-5. Colin Montgomerie is part of that logjam as well after a second-round 68.
Defending champion Ernie Els posted a 3-under 68 and is tied for 24th at minus-4.
Jose Manuel Lara, the remaining first-round leader, managed a 75 on Friday and is part of group tied for 39th at 2-under-par 140.