Montgomerie, two over overnight, fell to six over and was in danger of missing the halfway cut after setting off again with a double-bogey seven and then dropping further strokes at the 16th and 18th for an outward 39.

The only change at the top was that Bob Estes joined fellow Americans Rocco Mediate and Olin Browne – late starters today – with three birdies in his first four holes. But they were followed by a double-bogey six on the 472-yard fifth.

Montgomerie was in perfect shape after two shots on the long 10th, but pitched into the guarding bunker, went over the green and saw his putt up the slope fail to make it.

After his next attempt he was left with a six-footer to avoid an eight and he did well to make that one.

It was not until the difficult 16th – a hole where he was one of only four players to birdie yesterday – that he missed a fairway, but having found a bunker there he came up short of the green and failed to hole from eight feet.

When he bogeyed the 442-yard 18th for the second day running, almost putting off the green, he was down in joint 80th spot, but his presence over the weekend could be saved under the rule whereby anybody within 10 strokes of the lead survives.

Mickelson’s problems began immediately too and he did wonderfully well to escape from the 10th with a five.

From the edge of the rough he went with a fairway wood, but it finished under the lip of a bunker 80 yards short of the green. He opted to splash out into thick rough and played a great pitch to five feet.

It was a sign that all was not well with the world number three, however, and he could not recover from the rough on the 12th and 13th, then took three from the edge of the short 15th, came up short on the next and three-putted the 17th.

New Zealander Michael Campbell was having a much better time. After missed cuts on his last four appearances in the event – they included rounds of 83, 80 and 78 – the 36-year-old, who came through the European qualifier with a last-hole birdie at Walton Heath last week, turned in 34 and when he birdied the long 10th he was up into a share of fifth spot.

Vijay Singh’s outward 35 kept him well-placed at level par.

None of the top four players had returned to the course yet, defending champion Retief Goosen and England’s Lee Westwood being two under overnight, and Luke Donald (one under) and Tiger Woods (level) had a lie-in as well.

Padraig Harrington, teeing off again already seven over, parred the first seven, but then bogeyed the eighth and 11th to be in serious danger of his first missed cut in the championship since his 1997 debut.

Fellow Dubliner Paul McGinley was seven over with six to play, while Scottish debutant Stephen Gallacher dropped from nine over to 13 over in the first six.