Clarke snatched the lead with a 66 for a two-round aggregate of 133, 11 under par, with Montgomerie and Van de Velde, just one behind after both men had shot a second successive 67.
Montgomerie stressed that being in contention week in and week out was a tiring business. The Scot, winner of the PGA last Monday, said: "I've been in contention now three weeks running and it does take it out of you. It's nice to be in contention but in some ways I feel you have to be fresh to win but we'll see what happens over the next few days.
"I'll be trying my hardest, obviously, because I know if I do win I'll go to the top of the Order of Merit after just four events. That's my goal. I want to get to the top of the Order of Merit as quickly as possible."
Clarke, winner of the Benson and Hedges tournament just two weeks ago, had a completely opposite view.
The Ulsterman is five years younger than Montgomerie at 29, but when told of the Scot's views on being in contention he said: "I'm where I want to be in tournaments, up there contending for our bigger events and this is one of them. I'm not tired at all. I'm very keen, very eager, to get myself into this position as often as possible."
Midway through the morning a thunderstorm caused a three-hour suspension, which led to Clarke making one of only two mistakes in his round. Starting at the 10th, he had had two birdies plus an eagle three at the 17th before his first error, at the 18th, where he was bunkered in two and did not get up and down.
But he then birdied the first and second to go to 10 under and had just driven off at the long third when the players were brought into the safety of the clubhouse.
As Clarke explained later: "It was a par five and I needed a three iron to reach the green in two. But after the rain my ball was wet and heavy and in a tight lie and I decided to hit a two iron which I hit into the water in front of the green. Fortunately after dropping out I played a good pitch to get up and down to save par." Another birdie at the long sixth took Clarke to 11 under and he finished with three pars to take his one shot lead.
Montgomerie made only one error, when he struck a bad wedge shot at the sixth and took a bogey six but he had six birdies on his card and finished reasonably satisfied for a man who always demands perfection.
Van de Velde had an up and down round with five birdies, one eagle and two bogeys and said that he was exhausted at the end.Reuse content