England 4 for 180 (Cook 72) trail Australia 385 (Smith 111, Warner 60, Broad 3-100) by 205 runs
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Hard though they tried, Alastair Cook and England could not shake Australia in Perth, on an enthralling day that produced some of the most compelling cricket of the Ashes series so far.
Knowing one more batting capitulation would all but hand the Urn to the hosts, England fought bravely with the ball then the bat but by day's end maintained only a tenuous hold on a match they cannot afford to lose.
The tourists' fight was personified by their captain's innings, a calm, collected 72 by Cook that nonetheless fell short of the definitive tally he desired. His exit at the hands of Nathan Lyon followed a lively spell by Mitchell Johnson, who then made another critical contribution to the series by leaping at mid-on to catch Kevin Pietersen from the bowling of a revved up Peter Siddle.
Ian Bell and Ben Stokes survived to the close, but they still have an enormous task ahead to reach parity on a pitch showing signs of deterioration in addition to its high pace and sharp bounce.
Australia's bowlers have been drained by their efforts on another day of temperatures nudging 40C but they remained an admirably skilful and united ensemble as the shadows lengthened, giving the batsmen barely a moment's peace.
England's frustrations on a tour where little has gone right for them was epitomised by the exit of Joe Root, who was flabbergasted to be given out caught behind as hard won gains were eroded. Reviewing the decision immediately, Root was ultimately sent on his way after video evidence could not mount a strong enough case for Tony Hill to overrule the on-field call of Marais Erasmus, despite Hot Spot revealing no mark on Root's bat and Real-Time Snicko finding a noise only after ball had passed bat.
England's bowlers had rounded up Australia's tail for the addition of 59 runs from their overnight 6 for 326. Stuart Broad and James Anderson pursued a fuller length than that of the first day and were rewarded with a series of edges that either found the slips cordon or squeezed through gaps - few runs were found anywhere else.
- England's current run-rate of 2.64 runs per over is the fifth-slowest in a Perth Test (with a minimum of 50 overs) since 2000. It's England's slowest in Perth since 1982.
- The dot-ball percentage in Australia's innings was 75%; in England's innings so far it's been 84%.
- Peter Siddle dismissed Kevin Pietersen for the tenth time in Tests - his average against Pietersen is 16.70. No other bowler has dismissed him more than six times in Tests.
- The 85-run first-wicket stand between Alastair Cook and Michael Carberry is England's highest for the opening wicket since March this year, when Cook and Nick Compton added 231 against New Zealand. In 21 innings in between, England's average stand for the first wicket was 23.95.
- Pietersen became the fifth England batsman to go past 8000 Test runs. He achieved it in 176 innings, the quickest among them. The previous-fastest among England batsmen was Graham Gooch, in 189 innings.
Johnson was out to his second ball of the morning, snicking a beautifully pitched delivery from Broad that curved subtly in before seaming the other way and going through to Matt Prior. Steve Smith could add only eight to his overnight 103, getting the merest of inside edges to an Anderson ball that moved back at him.
Erasmus declined the appeal but the evidence of Hot Spot and Real-Time Snicko was enough for the decision to be reversed by Hill under the DRS. Smith walked off shaking his head. Harris and Siddle also perished to edges though not before he and Lyon added a pesky 31 for the last wicket.
Cook survived a difficult diving chance offered to Smith's left from Harris before lunch, and after it Carberry's skied pull shot that landed inches beyond the grasp of a sprinting Haddin. Gradually the England openers wrested the initiative, forcing Australia onto a less aggressive footing, bowling for maidens to slow the run rate.
But the tactic proved extremely effective. Carberry was becalmed and played Harris onto his stumps while trying to leave the first ball delivered from around the wicket. Root's debatable feather to Watson drew raucous celebrations from the Australian huddle, and it was the hosts who went to tea feeling happier about their afternoon's work.
Both sides recognised the importance of the evening session, England wrestling for a foothold, Australia straining equally hard to turn them back. Pietersen and Cook withstood some exceptional bowling by Siddle, Harris and Johnson on resumption, concerning themselves principally with survival in the hope that things would get easier.
In the unrelenting heat, Clarke had to rotate his bowlers frequently but they responded by maintaining discipline in a way that offered little respite to the batsmen. The importance of the moment was emphasised when Clarke actively encouraged the crowd to get behind the pacemen, drawing an extra spell of speed out of Johnson at a moment when Cook and Pietersen might have wriggled free.
The din of Australian spectators around the WACA was rewarded as Cook eventually succumbed when Lyon's extra bounce drew a top-edged cut shot that Warner held diving forward at point. Having contributed to Cook's departure, Johnson made way for Siddle, pursuing his favoured quarry, Pietersen.
Australia's planning to Pietersen has succeeded in corralling the most free-spirited of batsmen, and he again perished to Siddle. This time it was not the midwicket trap but a toe-ended pull to mid-on that did for him, Johnson leaping with wonderful athleticism to claim the catch. Siddle's celebration was all bared teeth and spinning eyeballs.
Daniel Brettig is an assistant editor at ESPNcricinfo. He tweets here