He was also, however, three behind another of the home contingent Nick Watney, who despite a closing bogey shot 66 for 13 under and remained the likeliest of the trio to become the sixth first-time winner in the last seven majors.

Woods, still searching for former glories, was only 31st after a 72 – he had to birdie the last two holes just for that – and Mickelson down in 48th place following an even more disappointing 73.

McIlroy, five under at halfway, birdied three of his first five holes and after a slip on the eighth picked up the pace again on the back nine.

Further birdies came at the 10th, 13th and long 16th, the last of them lifting him out of a group containing German Martin Kaymer, Australian Jason Day and, most surprising of all, China’s Liang Wen-chong, who set a new course record with a sparkling 64.

“I’m not going to be over-aggressive and stupid, but you are going to have to give yourself plenty of chances,” said McIlroy, third in the event last year and at The Open last month.

“I feel as if I’ve got to shoot something in the mid-60s, but you never know.

“You could go out and shoot a great score and Nick plays well and that’s it.”

Watney, who needs a top-four finish to have a chance of a Ryder Cup debut at Celtic Manor in October, took charge with five birdies in his first seven holes as halfway pacesetter Matt Kuchar faltered.

He also bogeyed the eighth, but had three inward birdies before coming unstuck at the 500-yard last – a hole England’s Simon Dyson (joint 14th after a 68) described as “probably the hardest finishing hole I’ve played in my life”.

The 29-year-old may not be well known overseas, but he was seventh in The Masters and at St Andrews – and it took Phil Mickelson to deny him a world championship title last season.

The day’s play began with the completion of the second round – and the story of the morning had centred on Padraig Harrington, who was distracted by a photographer as he hit his second shot into the hazard short of the 18th green and double-bogeyed to miss the cut by one.

In any circumstance it was a bitter blow for the 2008 champion, but this time it had Ryder Cup implications.

Harrington, Luke Donald and Justin Rose all bowed out and that could leave the trio and Paul Casey – three under with a round to go – in a queue for Colin Montgomerie’s three wild cards in a fortnight.

That may look ample time for the situation to change, but all four want to stay in America rather than return to Europe for the last two qualifying events there.

“It’s very disappointing, but it would be silly to think that my last shot is going to cost me my place,” said Harrington.

“The Ryder Cup does come first. I made out my schedule to peak for the four majors and the Ryder Cup and I’m going to stick with it.

“If I get picked I want to be ready to play.”

Harrington admitted he was burnt out after winning the last two majors of 2008 - and he has not won a game in the last two Ryder Cup matches.

Woods, in addition to managing only one birdie on the front nine all week, was one over par for the four par fives and commented: “Tell me about it. I haven’t played them well all week. You’ve got to make birdies on the par fives and I haven’t done that.

“Ironically enough today I hit the ball better than I did the first two. I made nothing. You have to putt.

“But my swing feels a lot better. It’s not like I’m working on eight different things.”

He needs a top-14 finish this weekend just to have a chance of qualifying automatically for the Ryder Cup, but with so many Americans near the top of the leaderboard it is likely to require a much higher placing than that.

It is hard to imagine captain Corey Pavin not picking the world number one if necessary and, with Mickelson and Steve Stricker down the field too, Woods does at least look like retaining that top spot for a while longer.