A sub-aqua unit spent much of yesterday in a dingy on the River Rye, the waterway that runs along the length of the 18th hole here on the Montgomerie Course at Carton House, outside Maynooth.

It was an entirely appropriate scene, given that competitors in this latest edition of the Nissan Irish Open have encountered conditions that, if not exactly life-threatening, have been a test of survival, with the weather decreeing that the half-way stage of this €2.2 million tournament has yet to be reached.

If we shouldn't be surprised that a so-called Irish summer, albeit one in its decided early phase, should conspire to produce conditions more indicative of darkest winter, the upshot is an unconventional leaderboard. Sadly from an Irish perspective, it's one with only the barest hint of a chance to end the drought since John O'Leary became the last home winner of this event, back in 1982.

On a day significantly improved on Thursday's opening mix of high winds and rain, at least yesterday's offering enabled just over half of the field to complete their second rounds. Nicolas Colsaerts, a 23-year-old Belgian without a win on the European Tour, emerged as the rather surprising leader on four-under-par 140.

Although a number of forward tees were used to make for a less penal challenge, the course - and the conditions - still proved too great for many players, and the projected cut of four-over would be among the highest on tour this season.

With dusk descending, the claxon to signal the end of play came at 9pm. By then, Colsaerts, who had followed up his 73 with a 67, had long since finished, as had two of his three chief pursuers, Anthony Wall and Christian Cevaer, who were a shot further adrift.

In the fading light, Ian Poulter birdied his last hole to also finish just a shot adrift of the Belgian. When play finished for the night, there were 50 players left to complete their second rounds.

Colsaerts, for one, was relieved to have found the sanctuary of the clubhouse on 140. "Here, on this course, you have to grind it out and try to keep your head on. You can make bogey on almost every hole," he remarked.

Colsaerts - as well as Wall and Cevaer - benefited from the kinder side of the draw, and among those less fortunate on the opposite side destined to miss the halfway cut were course designer Colin Montgomerie, who, despite birdieing his closing hole, had a 72 for 149.

Among the likely Irish casualties was Graeme McDowell, who had a second successive 73 to be on six-over, 150.

Yet Colsaerts was not alone in demonstrating that there was a way to beat the course. Thomas Bjorn, more than anyone, proved the point with a course record-equalling 66, which left him on level-par 144. It was one of nine sub-70 rounds returned despite the severe test. And Poulter birdied four of his last six holes for a 70 to be on 141.

Padraig Harrington was on the 18th fairway when the claxon sounded, but opted to finish out his round, closing with a par five for a 74 that left him on one-over-par 145.

Peter Lawrie assumed the role of leading Irishman by birdieing the 18th for a 68, to reach the midway stage on one-under par 143. Starting out with a bogey on the first, Lawrie contrived to keep another dropped shot off his card and secured birdies on the sixth, ninth, 13th, 15th and 18th in a fine round of golf.

Others could be extremely satisfied with their day's work, among them Damien McGrane. At one stage in his round, as he walked to the 15th tee, his seventh hole, McGrane had fallen to five-over for the tournament.

However, a birdie on the 18th ignited his round. He wasn't to drop another shot and, in covering the front nine (his back) in 32 strokes, with four further birdies, he posted a 69 for level-par 144.

"All of a sudden I was able to hit the ball closer to the pins, able to hole a few putts," said McGrane, as if the deed were as simple as switching on a light bulb. "If you're playing golf and you are not 100 per cent you sort of hit weaker efforts all the time. In those situations, it is hard to make birdies. You might make a few pars, but you don't make birdies on a course like this."

McGrane, though, dug deep. He ground out a score, following up his birdie on the 18th by holing from a bunker for birdie on the first. From struggling to make the cut, he moved into contention with further birdies on the fourth, from 10 feet, and the sixth from 12 feet. He also birdied the seventh and the ninth, holing from five feet.

"I became more positive, hitting shots close to the flag rather than to 20 feet. That's the name of the game," said the Meath man.

For Darren Clarke, however, a second round 70 for one-over 145 didn't bring any great deal of contentment. "I'm deriving no pleasure whatsoever from playing golf, it's horrific," he said, adding: "I couldn't be bothered any more. I'm fed up with it. I'm not interested, couldn't be bothered."

Understandably, given his wife's illness, his heart and mind are elsewhere. The wonder of it all is that he is just five shots off the leader heading for the midway stage.