Ashley Giles shrugged off a stressful week to make a telling contribution to a determined bowling display which established England's dominant position in the crucial second Ashes Test.

Warwickshire's left-arm spinner has spent the week since Australia's 239-run opening Test defending himself from the criticism he viewed as "a witch-hunt" in the aftermath of England's capitulation at Lord's.

But given the stage to prove his worth to England's line-up and their Ashes challenge on an Edgbaston wicket wearing enough to interest the spinners, Giles used that built-up frustration to deliver an influential display and establish a crucial advantage on the second day.

Giles claimed three crucial wickets and ended two key partnerships as Australia were dismissed for 308 to concede a 99-run first innings deficit, which was increased to 124 after England reached 25 for one in the remaining seven overs before the close.

He had already made his mark by claiming the crucial wicket of Australian captain Ricky Ponting in the morning session, but it was his switch to the City End for an unchanged 21 overs spell that really strengthened England's stranglehold after he exploited signs of turn and uneven bounce.

His display was greeted with increasing enthusiasm by an England side protective of their highly-criticised team-mate, who have collectively responded superbly to the comprehensive beating they received at the start of the series.

Given a flying start by Matthew Hoggard, who removed Matthew Hayden for a duck when he picked out Andrew Strauss at short extra cover to the seventh ball of the day, England's seamers perhaps should have provided the biggest threat with cloud cover to help their efforts.

But instead of their impressive array of seamers providing the main threat, the much-maligned Giles stepped forward and demonstrated why he is so highly valued by captain Michael Vaughan with wickets at crucial times.

It was Giles that Vaughan turned to at the first sign of crisis during the morning session when determined opener Justin Langer, who endured blows on the helmet and in the stomach from Steve Harmison during the early overs, teamed up with Ponting and forged a threatening 88-run stand.

Ponting had been the dominant force during that partnership, contributing 61 off only 76 balls having almost been run out before he had scored when Kevin Pietersen's throw narrowly missed the stumps at the non-striker's end and flew for four overthrows.

Given that reprieve, Ponting made the most of his opportunity and punished England's wayward seam attack early on for 12 boundaries and seemed on course to register the fifth Ashes century of his prolific career.

That landmark was denied him, however, when he attempted to sweep Giles in his third over from the Pavilion End and instead gave a leading edge to Vaughan at short fine leg, prompting extended celebrations from England at Giles' success.

Ponting's demise was followed by the crucial scalp of Damien Martyn, a batsman made for such a situation, when he was brilliantly run out by Vaughan from mid-wicket attempting a quick single.

Despite his early success from the other end, Giles was switched to the City End after the interval and quickly began sowing seeds of doubt into Australia's minds which prompted a collapse of England proportions when they lost their last seven wickets for 114 runs in 21 overs.

The key to that demise was the loss of Michael Clarke, who had played cautiously but positively in contributing 40 to a 76-run stand with Langer but pushed forward with an angled bat to Giles and wicketkeeper Geraint Jones claimed a smart catch standing up to the stumps.

With Giles exerting an increasing influence from one end, Vaughan was able to blast away with his seamer's with the other and alternated all-rounder Andrew Flintoff and Simon Jones to great effect.

Flintoff dismissed Simon Katich, who provided a stubborn obstacle to remove at Lord's during his second innings 67, with his first delivery over the wicket which he edged behind and claimed the first of three useful wickets.

But it was the useful spell produced by Jones, reversing the ball to good effect, which finally broke Australia's resistance and ended Langer's innings spanning nearly four and a half hours and 18 runs short of the first century of this Ashes summer.

Langer had added 54 crucial runs with Adam Gilchrist to suggest a partnership which could hold the key to the outcome of this Test when he was given leg before to an inswinging yorker which may have missed leg stump.

Australia needed Shane Warne to bat responsibly and give Gilchrist the platform to guide them closer to England's total but was instead bowled charging down the pitch at Giles to leave the world's best wicketkeeper-batsman left with the tail-enders.

Jason Gillespie provided 36 minutes of defiance but Flintoff wrapped up the innings quickly with successive lbws to leave Gilchrist stranded on an unbeaten 49 after two hours at the crease.

With only seven overs before the close, Australia needed a spark of inspiration to give them hope of mounting a fightback and Warne provided it with his second ball, a sharply-turning leg-break which span almost the width of the wicket into Andrew Strauss' leg stump as he attempted to cover his stumps with a stride across.