Hundreds from Alastair Cook and Ian Bell put England on course to win the Ashes outright in Australia for the first time in 24 years.
Prolific opener Cook missed a second double-century of the series by just 11 runs but ticked off another clutch of Ashes run-scoring milestones nonetheless.
Bell (115), with whom Cook shared a crucial sixth-wicket stand of 154, finally added the first Ashes century of his career in an England total of 488 for seven and lead of 208 at stumps on day three at the SCG.
Requiring only a draw to close out series victory, the odds were therefore stacked in the tourists' favour.
Each of their centurions survived one conspicuously anxious moment.
Cook's came on 99 during the morning, when he rightly survived an incident which had echoes of a similar close call during his match-saving 235 not out in the first Test at Brisbane.
Unlike there, when Cook already had 209 to his name by the time Ricky Ponting claimed a low catch at midwicket, justice was clearly done after Phil Hughes initially appeared to get his hands underneath one at short-leg off Michael Beer.
Cook stood his ground, as he had back in November, and was vindicated when the umpires consulted video replays which demonstrated the ball had bounced.
Bell's escape was more marginal, and therefore more controversial.
On 67, he called for DRS after Aleem Dar gave him caught behind off Shane Watson. In the absence of compelling Hot Spot evidence to support the decision, it was overturned only for 'Snicko' to indicate several minutes later - it's not part of the DRS due to the time it takes to put together - that there had been an inside-edge after all.
Cook was already gone, having got a thick edge low to gully on a push-drive at Watson - ending a a 342-ball stay which brought him 16 fours and took his crease occupation for the series beyond 36 hours.
He has also put himself second in England's all-time list - behind only Wally Hammond, more than 80 years ago - of record runscorers in a Test series, with a tally of 766. He has more than 1,000 runs in his 15 first-class innings on this tour.
Cook's earlier reprieve meant Beer was once again denied a maiden wicket, a late no-ball verdict having stopped him opening his account when the same batsman mistimed him to mid-on on day two.
But the slow left-arm debutant did not have to wait much longer, before the out-of-form Paul Collingwood got him started when he aimed to hit over the top but fell to a steepling catch at mid-on by Ben Hilfenhaus.
After the morning loss of nightwatchman James Anderson, bowled off stump playing the wrong line to Peter Siddle, plenty was needed from Cook and Bell to ensure a mid-match advantage.
Cook would have been run out for 129 had Mitchell Johnson hit the stumps after turning round in his follow-through in an attempt to cut off an unwise single into the off-side in the final over before lunch.
That apart, though, a seamless stand - on a pitch probably at its best for batting - was characterised by ever increasing assurance from Cook and a succession of high-class shots from Bell.
The sixth-wicket pair sapped Australia's energy and spirit in a wicketless middle session and, although Cook went soon after tea, Bell came through one more scare on 84 when Steve Smith failed to hold a fiercely-hit caught-and bowled chance to reach three figures in 209 balls.
Matt Prior also aided the England cause with a typically fluent contribution to a century stand with Bell, whose moment of celebration was accompanied by Australian boos as well as English cheers.
Prior reached 50 with a square drive, but Bell finally fell shortly after as he edged Johnson to Clarke in a floating slip position, ending a partnership of 107.
Tim Bresnan joined Prior at the crease but faced just seven balls before the umpires took the players off for bad light, leaving the wicketkeeper unbeaten on 54 off 59 balls.