Our man at Wentworth

Montgomerie's birdie putt lipped out on the 34th while Hensby sunk his to go two up, and a par at 17 ended the tie.

Top seed Retief Goosen romped to an 8&7 victory over England's Kenneth Ferrie.

Luke Donald demolished Bernhard Langer 7&6, Paul McGinley crushed Thomas Bjorn 6&5 and Jose Maria Olazabal ousted David Howell at the 36th hole.

Montgomerie, making his 12th appearance in the event, surged four ahead after 13 holes and finished the morning session three up.

However, he lost his form and carded bogeys to lose the 19th, 21st and 22nd.

Since the Open there haven't been the performances that I have been looking for Colin Montgomerie More quotes from Wentworth

Hensby pounced on Monty's slump to take the lead for the first time at the 28th with an eight-foot birdie putt and held on to set up a quarter-final against Goosen.

"I rimmed a whole lot this afternoon and didn't win a hole and under those circumstances you probably don't deserve to win," said Montgomerie afterwards.

"He played a lot better this afternoon than he did this morning but overall I played well but didn't score well enough.

"You need to be more under par than I was today and overall I didn't score well enough."

He added: "Since the Open there haven't been the performances that I have been looking for.

"I have had only one top 10, or one finish really, and that has been disappointing. Never mind, we'll get back into it."

Hensby said: "I kind of took advantage of the situation. Then I made some nice putts at the right time and I just didn't let up.

"Once I got one-up, I really didn't give him a break," said Hensby.

Goosen in action at Wentworth

Goosen bogeyed the first to allow world number 109 Ferrie to take a surprise lead.

But the South African levelled immediately and took a two-hole lead by the turn after holing from 14 feet at the sixth and chipping in from 20 feet on the eighth.

Three more birdies followed as he extended the lead to five, but Ferrie birdied the long 17th to give himself some hope in the afternoon.

However, Goosen claimed the first hole of the afternoon and the match finished when he won his third hole in four at the 29th.

England's Donald enjoyed the best start against Germany's Langer, the man who gave him his Ryder Cup debut last September.

Donald won four of the first six holes and had to birdie only one of them as the 48-year-old Langer, who made his debut back in 1981, bogeyed the first, third and sixth.

Langer lost further ground after bogeying the 19th and 20th and Donald soon wrapped up victory to set up a quarter-final match with McGinley.

I was the last man in and hopefully I'll be the last man standing Paul McGinley

"My only bogey was a three-putt. I didn't do a lot wrong," said the Englishman.

"We have very similar games and I can learn a lot from Bernhard. He never forces shots and plays within himself."

Ireland's McGinley fought back to beat Wentworth neighbour Thomas Bjorn 6&5 after the Dane suffered a nightmare run.

Bjorn was one up through 22 holes, but lost seven of the next eight - a run which included McGinley sinking an 85-yard pitch for an eagle two at the 29th.

"I was the last man in and hopefully I'll be the last man standing," said McGinley. "Maybe fate and destiny is on my side."

Olazabal rolled in 35-foot birdie putts at the sixth and eighth to be three ahead of Howell, but the Englishman fought back in a keenly-contested match.

However, the Spaniard clinched it with a magnificent closing eagle three to line up a match with Angel Cabrera after the second-seeded Argentine finished two up on Trevor Immelman.

US Open champion Michael Campbell of New Zealand went six up but in the end squeezed past Australia's Geoff Ogilvy by one hole.

He will face Steve Elkington, another Australian, in the quarter-finals after he beat South Africa's Tim Clark 6&5 after racing into a five-shot lead.