Three weeks after he pulled out of a tournament in Germany to celebrate Rory McIlroy's runaway US Open win, the 42-year-old shares the halfway lead in The Open Championship with American Lucas Glover on four under.

Adam Scott is the best-placed of the Australians after day two, sitting in equal 14th at one under, just three shots off the pace. Richard Green, Jason Day and Robert Allenby all sit on one over after 36 holes.

is next on one over following a day that also saw Luke Donald and Lee Westwood, the world's top two, both crash out.

Clarke has not had a top-10 finish in a major for a decade, but a second successive 68 at Royal St George's takes him into the weekend on four under.

And with the two first day pacesetters, English amateur Tom Lewis and Dane Thomas Bjorn, having rounds of 74 and 72 respectively, it is the hero of the 2006 Ryder Cup who will occupy centre stage when he tees off on Saturday.

Two won't be on the stage at all over the weekend are Donald and Westwood.

Donald, who hoped his four-shot victory in the Scottish Open would lead to his first major triumph, bogeyed the last four holes to miss by three on six over.

Westwood waited seven hours until nearly 8.30pm to learn that his four-over aggregate was one too many.

They must try again at next month's US PGA Championship in Atlanta, but have no further interest in what happens in Kent.

Clarke is two rounds from possibly joining a major club that includes not only McIlroy, but also their fellow Northern Irishman Graeme McDowell and Dubliner Padraig Harrington, the man who got the ball rolling when he had back-to-back Opens and then a US PGA as well.

Lucky to be out in the calmer conditions on day two, he owes his place in his 20th Open to taking the 30th and last exempt spot off last year's European Tour money list by less than 2,000 pounds.

A double bogey on the fourth, where a chip came back down a steep slope, was cancelled out by an eagle putt of around 80 feet three holes later.

Four birdies and three bogeys followed, but he had the lead in the clubhouse on his own for a mere 10 minutes. Glover was in the following group.

Lewis saw 61-year-old playing partner Tom Watson claim a hole-in-one at the sixth in the day's most electrifying moment, but, by scoring nine more than his lowest ever round by an amateur in the event, the 20-year-old dropped out of the top 10.

Bjorn is now joint third with Spain's Miguel Angel Jimenez, German Martin Kaymer and American Chad Campbell.

Most early eyes had been were on Young Tom and Old Tom - Lewis and five-time champion Watson.

Watson's ace with a four-iron was the 15th hole-in-one of his life, hopping in on the first bounce.

The 2009 runner-up - he would have been the oldest major champion by 11 years if only he had parred the final hole at Turnberry - continued to amaze with a 70. On two over he made his 24th Open cut and extended his own record as the oldest man to play all four rounds.

McIlroy remains a threat at level par after a 69 and Phil Mickelson too on one under.