After trailing by one overnight, Montgomerie looked in imperious form in signing for a second superb 68 in a row to move three clear of two-time Senior Masters champion Carl Mason on eight under par, while Scotland's Ross Drummond is a shot further back with 18 holes to play at Woburn Golf Club.
Montgomerie, making just his third appearance on the Senior Tour and chasing his first professional victory since the 2007 European Open, revelled in the conditions which saw blue skies but a swirling wind, bouncing back from an bogey at the par-5 first with six straight pars. It was at the par-4 eighth, though, that his round caught fire, holing a 30-foot birdie putt to kick-start a run of six birdies in what was a true masterclass in iron-play.
"I didn't really have to make one putt in that run after holing that long one at the eighth," said Montgomerie. "So my irons are good, it's just a question of getting into the right positions and then trying to take advantage. It would mean an awful lot to win. I haven't won for a long time, six years, so it would be very special if I can go on and complete the job."
At the Wales Open, American Peter Uihlein can give himself a belated birthday present worth £300,000 with a second European Tour title of the season today. Uihlein, who turned 24 on Thursday, carded a third-round 67 at Celtic Manor to finish seven under par and claim a three-shot lead over French pair Thomas Levet and Gregory Bourdy.