Colin Montgomerie Opens two shot lead - Johnnie Walker Championship 2006

Sweden's Robert Karlsson (68), Dane Soren Hansen (70), Marcus Fraser of Australia (68) and Britain's Andrew Marshall (67) are a further stroke behind, but overnight leader Thomas Bjorn slipped four shots off the pace after a 75.

Despite hauling himself to the top of the leaderboard, Montgomerie, who was presented with a birthday cake with after his round, had another mishap on a finishing hole.

On Sunday, he lost the U.S. Open by double-bogeying the 18th at Winged Foot and in the first round at Gleneagles he bogeyed the last to miss out on a share of second place overnight.

This time, he missed a three-foot birdie putt to deny himself a larger leading margin. Having gained his final green in two at the par-five finish, Montgomerie three-putted from 20 feet.

"I just don't know what's going on here," said a perplexed Montgomerie after signing for a round that contained six birdies and one bogey.

"That's my third round in a row and that's not good at all.

"If I can't two-putt from 20 feet there's something wrong. There was nothing difficult about it at all.

"I've got to get it right for 18 holes. It tarnished the U.S. Open, it tarnished yesterday and it's tarnished today."

His final blemish excepted, Montgomerie was happy to be leading when last year he had only survived 12 holes of the tournament before retiring with bruised fingers.

Following a week where the eight-times European number one had his usual confrontations with the American gallery, there was a more lighthearted moment at Gleneagles.

Montgomerie's caddie Alastair McLean had barked out the usual command, "Quiet", as his player stood over a chip, when a young voice in the crowd shouted back: "You keep quiet".

"It's the first time I've been answered back," said Montgomerie. "What could you say? The lad was two years old."