Patrik Sjoland of Sweden shot a 64 to share second place with the English duo of David Gilford and David Lynn at 11-under-par 133.
Havret played the back side first at Simon's Golf Club and promptly birdied the 10th. He then collected three consecutive birdies starting at the par-4 16th to make the turn at 8-under.
The 26-year-old notched a birdie at the par-3 second and began his move to the top of the leaderboard with a birdie at the par-4 fifth.
Havret then birdied the sixth and ran home a 10-foot putt for a birdie at the par-5 seventh.
At the par-4 eighth, Havret, whose lone victory on the European Tour came at the Italian Open in 2001, hit his second shot to 18 feet and drained the putt to make it four in a row.
'I was struggling after winning in Italy,' said Havret. 'I wanted to make my game more consistent and did a few things wrong.'
Despite the stellar bogey-free round, Havret came up one shot short of the course record. Havret's countryman Raphael Jacquelin established the mark of 62 in the opening round.
'Just a few months ago we were both struggling and he had some great finishes,' Havret said of Jacquelin. 'Golf is like that but we have kept trying together and maybe now it's my turn.'
Jacquelin, who is playing with his girlfriend as his caddie, had a much different round on Friday. Like Havret, Jacquelin started on the 10th and found trouble at the very next hole.
The 29-year-old double-bogeyed the par-4 11th but managed to recover with a birdie at the 12th. Jacquelin struggled again with a birdie at the third but tallied back-to-back birdies from the fourth for a round of 72.
Jacquelin finished three shots off the lead at 10-under-par 134 along with Jonathan Lomas, Kevin Na, Andrew Raitt, Philip Archer, Brian Davis and Tobias Dier.
Montgomerie picked up two birdies on the inward half for a round of 65. He was joined by Andrew Coltart, Miguel Angel Jimenez, Peter Lawrie and Ian Poulter at 9-under-par 135.
'This is a good position. Ideal in fact,' said Montgomerie. 'Obviously I needed another low score but I just have to hole some putts over the weekend and I should be right there. I am looking forward to it.'
Local favorite Thomas Bjorn was one shot further back at 8-under-par 136 along with fellow Dane Peter Jespersen. They were joined by Philip Golding and Stephen Gallacher in a tie for 17th.
'I am playing well enough but this is probably the worst I've putted for six to eight weeks,' said Bjorn. 'I am playing solid golf. I just need one low round over the weekend to get myself in there and when I do that, I normally do well.'
The 36-hole cut fell at 3-under-par 141 and among those who survived on the number was Graeme McDowell. McDowell picked up an ace at the par-3 14th that not only gave him a chance to play the weekend but a brand new car as well.