England were 185 for seven at tea — having been 47 for five — after the 18-year-old Aamer, in his 14th match at this level, had become the youngest bowler to take 50 Test wickets.
Their total owed much to Trott’s well-made 77 not out during an innings where most of the England top-order failed to cope with the swinging ball.Trott found a useful ally in Stuart Broad (46 not out).
England’s eighth-wicket pair had so far added an unbroken 83, with Broad, who bats left-handed, driving stylishly through the offside and hooking Aamer for six.
Left-arm quick Aamer transformed England’s overnight 39 for one into 47 for five with a dramatic spell of four wickets for no runs in eight balls.
That haul saw him rip through England’s middle-order, with Kevin Pietersen, Paul Collingwood and Eoin Morgan — the Nos 4, 5 and 6 respectively — all dismissed by Aamer for nought.
England were 97 for five at lunch but soon afterwards they were 102 for seven as Aamer took two wickets for no runs in three balls.
Matt Prior, who helped Trott add 55 for the sixth wicket was caught behind by Kamran Akmal for 22 and Graeme Swann well held low in the gully by Azhar Ali for the fourth duck of the innings.
Nevertheless, Trott retained his composure to compile a 90-ball fifty with seven fours.
Pakistan, looking to square the series at 2-2 after victory at The Oval last week, did not have long to wait for a breakthrough on Friday after bad weather meant only 12.3 overs were possible on Thursday.
Aamer squared up Oval centurion Alastair Cook off Friday’s third ball and the left-handed opener was caught behind for 10.
