Second Test, Edgbaston (day two, close):
England 251 v Pakistan 72 & 19-1
Kevin Pietersen, who was dropped three times, was finally dismissed by Ajmal
Pakistan face a monumental task to avoid defeat after day two of the second Test against England.
The tourists are 19-1, 160 runs behind England's first-innings total of 251, with Azhar Ali (5) and Imran Farhat (10) unbeaten overnight at Edgbaston.
The hosts lost their final five wickets for just eight runs as spinner Saeed Ajmal (5-82) impressed for Pakistan.
Kevin Pietersen (80) enjoyed plenty of luck sharing a 133-run third-wicket stand with Jonathan Trott (55).
With batting looking increasingly difficult on a pitch offering discernable movement for England's trio of seamers, Pakistan must produce a remarkable rearguard action to prevent the hosts from taking a 2-0 lead in the four-match series.
Ali and Farhat survived a testing 15-over inquisition in the late Birmingham sunshine from James Anderson, Stuart Broad and Steven Finn.
But after captain Salman Butt had edged a wicked delivery from Anderson to Andrew Strauss at first slip, runs proved hard to come by and the feeling was that further wickets would come England's way.
Overall Saturday was a good day for Pakistan, but their first-innings deficit could have been significantly lower had they taken their chances in the field.
Yet again their amateur fielding was exposed with their quartet of bowlers looking increasingly beleaguered in the truncated morning session.
Ajmal enjoyed a day to remember, but Pakistan remain in trouble
Early morning showers restricted play before lunch to just 34 minutes, enough time for Pietersen to benefit from one of the most embarrassing drops seen at Edgbaston.
With his score on 36, the ex-England captain was trapped in front from the second over of the day by the impressive Mohammad Amir, but umpire Steve Davis ignored the appeal and instead fixed his sights on the path of the looping ball towards Umar Amin at gully.
The Australian official's gaze suggested the ball had rebounded off the inside edge of Pietersen's bat onto the front pad - confirmed by Hawk-Eye - but Amin somehow contrived to miss a catch almost impossible to fluff.
The reaction from his team-mates was of sheer disbelief. But more consternation followed in the following over when Pietersen attempted to back away in the final moments of Mohammad Asif's run-up, distracted by movement from batting partner Trott.
But instead of allowing the ball to pass, Pietersen courted controversy when he looped a half-hearted shot to mid-off, where Butt took a low diving catch.
The Pakistani captain's celebrations were immediately curtailed when umpire Marais Erasmus signalled a dead ball, much to Butt's chagrin.
Law 23.3.b (v) of the game states that "either umpire shall call 'dead ball' when he is satisfied that for an adequate reason the striker is not ready for the delivery of the ball and, if the ball is delivered, makes no attempt to play it".
Yet despite being dropped three times, caught off a dead ball and surviving numerous close lbw appeals, Pietersen brought up his 20th Test half century, his fourth this year, with a leg-glance through square leg for four.
At the other end, Trott batted with diligence and patience, compiling a 105-ball half-century with an authoritative straight drive off Umar Gul.
But the number three's tenure was brought to an end by part-time seamer Amin when Trott (55) cut a wide delivery to Yasir Hameed at gully, who was substituting for Shoaib Malik.
Pakistan's cause was further hindered when Gul was forced to leave the field with a hamstring tweak - an injury likely to rule the fast bowler out of the rest of the series.
The overhead conditions once again intervened with England 191-3, forcing a 95-minute disruption.
Play resumed at 1600 BST and England's innings soon subsided. Pietersen lasted just 12 more minutes until, deceived by an Ajmal doosra, he lobbed a simple catch back to the off-spinner.
New batsman Eoin Morgan survived 15 deliveries before he edged a probing Mohammad Asif delivery outside off stump to wicketkeeper Zulqarnain Haider.
The dismissal set the stage for Ajmal, appearing in only his sixth Test match for his country, to rip through England's lower middle order.
Bowling around the wicket, Ajmal probed in and around off stump, creating uncertainty with his adroit change in pace and his array of variations.
Salman Butt argues with Marais Erasmus over the dead-ball incident
He collected his second wicket when Matt Prior misjudged a delivery from around the wicket, rapping him in front of the stumps with little hope of overturning umpire Erasmus' decision on the referral.
Ajmal, who saw Hameed drop Graeme Swann, snared Collingwood with the perfect doosra, caught by Imran Farhat at slip attempting to push the ball against the spin from around the wicket.
Stuart Broad survived three deliveries before flicking a sharp catch to Hameed at leg slip, while captain Butt grassed yet another dolly at mid-on to give Swann a third life.
However, Ajmal collected his first ever five-wicket haul in Test cricket when Swann top-edged a heave high into the air, with the bowler snaffling the catch for his second caught and bowled of the innings.
As overhead conditions cleared, giving way to cobalt-blue skies, Anderson collected his 16th wicket of the series when removing Butt.
And Ali, sweating on a pair, was reprieved by the referral system when replays suggested the ball had flicked his pad on the way through to wicketkeeper Prior off Broad.